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Retirement and Postemployment Benefits (Plan Assets and Expected Cash Flows) (Details) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jan. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016
Pension Plan [Member] | U.S. [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | $ 3,488 | $ 3,243 | $ 3,227 | $ 3,488 | $ 3,243
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,488 | 3,243 | 3,227 |  |
Balance at end of period |  | 3,488 | 3,243 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 65 | 79 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 0 |
Expected amount of benefit payments in the next period for non-qualified plans |  |  |  | 13 |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2018 |  |  |  | 260 |
2019 |  |  |  | 269 |
2020 |  |  |  | 268 |
2021 |  |  |  | 270 |
2022 |  |  |  | 272 |
2023-2027 |  |  |  | 1,328 |
Pension Plan [Member] | U.S. [Member] | Subsequent Event [Member] |  |  |  |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions | 145 |  |  |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] |  |  |  |  |
Assumptions Used in Calculations (Numeric) [Abstract] |  |  |  |  |
The limited lives of four partnership of private equity investments (in years) |  | 10 years |  |  |
The amount of potential liability that maybe required to be funded by the master trust during life of the partnership |  |  |  | $ 28 |
Number Of Days Notice Required To Redeem Shares |  | 45 days |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 100.00% | 100.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 100.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,561 | $ 3,381 | 3,381 | $ 3,561 | $ 3,381
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,561 | 3,381 |  |  |
Balance at end of period |  | 3,561 | 3,381 |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 716 | 714 | 714 | 716 | 714
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 716 | 714 |  |  |
Balance at end of period |  | 716 | 714 |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 931 | 909 | 909 | 931 | 909
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 931 | 909 |  |  |
Balance at end of period |  | 931 | 909 |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 37 | 40 | 42 | 37 | 40
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 37 | 40 | 42 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Purchases, sales and settlements |  | (4) | (3) |  |
Balance at end of period |  | 37 | 40 |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 301 | 181
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 301 | 181
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 229 | 152
Measured at fair value using net asset value per share |  |  |  | 364 | 272
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 229 | 152
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | International Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 538 | 551
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Commingled Debt Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 611 | 546
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 186 | 381
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 186 | 381
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 883 | 850
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 870 | 837
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 13 | 13
Fair value at end of period | 13 | 13 | 10 | 13 | 13
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 13 | 13 | 10 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 0 | 0 |  |
Purchases, sales and settlements |  | 0 | 3 |  |
Balance at end of period |  | 13 | 13 |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 10 | 8
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 10 | 8
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Real Estate Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 109 | 102
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Private Equity Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 80 | 80
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Hedge Fund Of Funds Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 175 | 167
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 50 | 61
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 50 | 61
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 1 | 3
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 1 | 3
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 24 | 27
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 24 | 27
Fair value at end of period | 24 | 27 | 32 | 24 | 27
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 24 | 27 | 32 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Purchases, sales and settlements |  | (4) | (6) |  |
Balance at end of period |  | 24 | 27 |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Receivables And Payables Net [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 72 | (15) | (15) | 72 | (15)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 72 | (15) |  |  |
Balance at end of period |  | 72 | (15) |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Account 401 H [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | (145) | (123) | (123) | (145) | (123)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | (145) | (123) |  |  |
Balance at end of period |  | (145) | (123) |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Not Including 401 H Assets [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,488 | 3,243 | 3,243 | $ 3,488 | $ 3,243
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,488 | 3,243 |  |  |
Balance at end of period |  | 3,488 | 3,243 |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 56.00% | 52.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 55.00% |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 32.00% | 30.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 14.00% | 12.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Alternative Investments [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 10.00% | 10.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 43.00% | 46.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 43.00% |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 39.00% | 43.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Derivatives [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 4.00% | 3.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Liquidity Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 1.00% | 2.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 2.00% |
Pension Plan [Member] | U.K. [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 100.00% | 100.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 100.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 8,490 | 7,211 | 7,625 | $ 8,490 | $ 7,211
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 8,490 | 7,211 | 7,625 |  |
Balance at end of period |  | 8,490 | 7,211 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 486 | 330 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 191 |
Recurrence of formal actuarial valuations (in years) |  | 3 years |  |  |
Percentage of deficit funding requirements permitted to recover in rates |  | 78.00% |  |  |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2018 |  |  |  | 343 |
2019 |  |  |  | 349 |
2020 |  |  |  | 353 |
2021 |  |  |  | 356 |
2022 |  |  |  | 362 |
2023-2027 |  |  |  | 1,843 |
Pension Plan [Member] | U.K. [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 216 | $ 42 | 42 | 216 | 42
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 216 | 42 |  |  |
Balance at end of period |  | 216 | 42 |  |
Pension Plan [Member] | U.K. [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,140 | 2,942 | 2,942 | 3,140 | 2,942
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,140 | 2,942 |  |  |
Balance at end of period |  | 3,140 | 2,942 |  |
Pension Plan [Member] | U.K. [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 0 | 0 | 0 | $ 0 | $ 0
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 0 | 0 |  |  |
Balance at end of period |  | 0 | 0 |  |
Pension Plan [Member] | U.K. [Member] | Cash And Cash Equivalents [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 2.00% | 1.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 0.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | $ 216 | $ 42
Pension Plan [Member] | U.K. [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 216 | 42
Pension Plan [Member] | U.K. [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.K. [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | $ 0 | $ 0
Pension Plan [Member] | U.K. [Member] | U.K. Companies Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 2.00% | 3.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 2.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 157 | $ 210
Pension Plan [Member] | U.K. [Member] | European Companies Excluding U.K. Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 1.00% | 2.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 1.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 98 | $ 177
Pension Plan [Member] | U.K. [Member] | Asian Pacific Companies Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 1.00% | 2.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 1.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 60 | $ 140
Pension Plan [Member] | U.K. [Member] | North American Companies Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 1.00% | 3.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 1.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 123 | $ 227
Pension Plan [Member] | U.K. [Member] | Emerging Markets Companies Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 1.00% | 3.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 1.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 62 | $ 209
Pension Plan [Member] | U.K. [Member] | Global Equities Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 16.00% | 6.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 10.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 1,335 | $ 466
Pension Plan [Member] | U.K. [Member] | Global Tactical Asset Allocation Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 33.00% | 33.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 41.00% |
Pension Plan [Member] | U.K. [Member] | Other Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 2,807 | $ 2,363
Pension Plan [Member] | U.K. [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 37.00% | 41.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 38.00% |
Pension Plan [Member] | U.K. [Member] | U.K. Corporate Bonds Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | $ 3 | $ 2
Pension Plan [Member] | U.K. [Member] | U.K. Corporate Bonds Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.K. [Member] | U.K. Corporate Bonds Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 3 | 2
Pension Plan [Member] | U.K. [Member] | U.K. Corporate Bonds Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.K. [Member] | U.K. Gilts Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 3,137 | 2,940
Pension Plan [Member] | U.K. [Member] | U.K. Gilts Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Pension Plan [Member] | U.K. [Member] | U.K. Gilts Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 3,137 | 2,940
Pension Plan [Member] | U.K. [Member] | U.K. Gilts Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | $ 0 | $ 0
Pension Plan [Member] | U.K. [Member] | Alternative Investments [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 6.00% | 6.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 5.00% |
Pension Plan [Member] | U.K. [Member] | Real Estate Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 492 | $ 435
Other Postretirement Benefits Plan [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 100.00% | 100.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 100.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 405 | 378 | 379 | $ 405 | $ 378
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 405 | 378 | 379 |  |
Balance at end of period |  | 405 | 378 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 15 | 19 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 14 |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2018 |  |  |  | 51 |
2019 |  |  |  | 51 |
2020 |  |  |  | 50 |
2021 |  |  |  | 49 |
2022 |  |  |  | 48 |
2023-2027 |  |  |  | 218 |
Expected Federal Subsidy (Details) [Abstract] |  |  |  |  |
Federal subsidy 2018 |  |  |  | 1 |
Federal subsidy 2019 |  |  |  | 0 |
Federal subsidy 2020 |  |  |  | 1 |
Federal subsidy 2021 |  |  |  | 0 |
Federal subsidy 2022 |  |  |  | 0 |
Federal subsidy 2023-2027 |  |  |  | $ 2 |
Other Postretirement Benefits Plan [Member] | Cash And Cash Equivalents [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 4.00% | 2.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 5.00% |
Other Postretirement Benefits Plan [Member] | Money Market Funds [Member] |  |  |  |  |
Assumptions Used in Calculations (Numeric) [Abstract] |  |  |  |  |
Number of months from date of purchase that investment must mature |  | 13 months |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 10 | $ 5 | 5 | $ 10 | $ 5
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 10 | 5 |  |  |
Balance at end of period |  | 10 | 5 |  |
Other Postretirement Benefits Plan [Member] | Money Market Funds [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 10 | 5
Other Postretirement Benefits Plan [Member] | Money Market Funds [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Other Postretirement Benefits Plan [Member] | Money Market Funds [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | $ 0 | $ 0
Other Postretirement Benefits Plan [Member] | Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 47.00% | 48.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 45.00% |
Other Postretirement Benefits Plan [Member] | United States Large Cap Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 123 | $ 123
Other Postretirement Benefits Plan [Member] | Commingled Debt Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | $ 96 | $ 114
Other Postretirement Benefits Plan [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 49.00% | 50.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 50.00% |
Other Postretirement Benefits Plan [Member] | Corporate Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 30 | 0 | 0 | $ 30 | $ 0
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 30 | 0 |  |  |
Balance at end of period |  | 30 | 0 |  |
Other Postretirement Benefits Plan [Member] | Corporate Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Other Postretirement Benefits Plan [Member] | Corporate Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 30 | 0
Other Postretirement Benefits Plan [Member] | Corporate Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Other Postretirement Benefits Plan [Member] | Municipalities Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 12
Other Postretirement Benefits Plan [Member] | Municipalities Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Other Postretirement Benefits Plan [Member] | Municipalities Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 12
Other Postretirement Benefits Plan [Member] | Municipalities Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Other Postretirement Benefits Plan [Member] | Receivables And Payables Net [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 1 | 1 | 1 | 1 | 1
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 1 | 1 |  |  |
Balance at end of period |  | 1 | 1 |  |
Other Postretirement Benefits Plan [Member] | Account 401 H [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 145 | 123 | 123 | 145 | 123
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 145 | 123 |  |  |
Balance at end of period |  | 145 | 123 |  |
Other Postretirement Benefits Plan [Member] | Total Trust Assets Not Including 401 H Assets [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 259 | 254 | 254 | 259 | 254
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 259 | 254 |  |  |
Balance at end of period |  | 259 | 254 |  |
Other Postretirement Benefits Plan [Member] | Total Trust Assets Not Including 401 H Assets [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 10 | 5 | 5 | 10 | 5
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 10 | 5 |  |  |
Balance at end of period |  | 10 | 5 |  |
Other Postretirement Benefits Plan [Member] | Total Trust Assets Not Including 401 H Assets [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 30 | 12 | 12 | 30 | 12
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 30 | 12 |  |  |
Balance at end of period |  | 30 | 12 |  |
Other Postretirement Benefits Plan [Member] | Total Trust Assets Not Including 401 H Assets [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 0 | 0 | 0 | 0 | 0
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 0 | 0 |  |  |
Balance at end of period |  | $ 0 | $ 0 |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | Master Trust [Member] |  |  |  |  |
Information About Plan Assets (Numeric) [Abstract] |  |  |  |  |
Undivided interest percentage in each asset category that PPL subsidiary holds |  | 40.00% | 41.00% |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 1,402 | $ 1,315 | $ 1,289 | 1,402 | 1,315
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 1,402 | 1,315 | 1,289 |  |
Balance at end of period |  | 1,402 | 1,315 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 21 | 66 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 0 |
Expected amount of benefit payments in the next period for non-qualified plans |  |  |  | 4 |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2018 |  |  |  | 109 |
2019 |  |  |  | 113 |
2020 |  |  |  | 114 |
2021 |  |  |  | 115 |
2022 |  |  |  | 116 |
2023-2027 |  |  |  | 573 |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Subsequent Event [Member] |  |  |  |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions | 105 |  |  |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] |  |  |  |  |
Information About Plan Assets (Numeric) [Abstract] |  |  |  |  |
Value of plan U.S. pension trust assets that relate to PPL subsidiary |  |  |  | 1,400 | $ 1,300
Assumptions Used in Calculations (Numeric) [Abstract] |  |  |  |  |
The limited lives of four partnership of private equity investments (in years) |  | 10 years |  |  |
The amount of potential liability that maybe required to be funded by the master trust during life of the partnership |  |  |  | $ 28 |
Number Of Days Notice Required To Redeem Shares |  | 45 days |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 100.00% | 100.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 100.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,561 | $ 3,381 | 3,381 | $ 3,561 | $ 3,381
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,561 | 3,381 |  |  |
Balance at end of period |  | 3,561 | 3,381 |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 716 | 714 | 714 | 716 | 714
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 716 | 714 |  |  |
Balance at end of period |  | 716 | 714 |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 931 | 909 | 909 | 931 | 909
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 931 | 909 |  |  |
Balance at end of period |  | 931 | 909 |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 37 | 40 | 42 | 37 | 40
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 37 | 40 | 42 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Purchases, sales and settlements |  | (4) | (3) |  |
Balance at end of period |  | 37 | 40 |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 301 | 181
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 301 | 181
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 229 | 152
Measured at fair value using net asset value per share |  |  |  | 364 | 272
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 229 | 152
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | International Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 538 | 551
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Commingled Debt Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 611 | 546
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 186 | 381
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 186 | 381
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 883 | 850
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 870 | 837
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 13 | 13
Fair value at end of period |  |  | 10 |  |
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period |  |  | 10 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 0 | 0 |  |
Purchases, sales and settlements |  | 0 | 3 |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 10 | 8
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 10 | 8
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Real Estate Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 109 | 102
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Private Equity Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 80 | 80
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Hedge Fund Of Funds Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 175 | 167
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 50 | 61
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 50 | 61
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 1 | 3
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 1 | 3
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 24 | 27
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 24 | 27
Fair value at end of period |  |  | 32 |  |
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period |  |  | 32 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Purchases, sales and settlements |  | (4) | (6) |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Receivables And Payables Net [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 72 | (15) | (15) | 72 | (15)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 72 | (15) |  |  |
Balance at end of period |  | 72 | (15) |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Account 401 H [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | (145) | (123) | (123) | (145) | (123)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | (145) | (123) |  |  |
Balance at end of period |  | (145) | (123) |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Not Including 401 H Assets [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,488 | 3,243 | 3,243 | $ 3,488 | $ 3,243
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,488 | 3,243 |  |  |
Balance at end of period |  | 3,488 | 3,243 |  |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 56.00% | 52.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 55.00% |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 32.00% | 30.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 14.00% | 12.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Alternative Investments [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 10.00% | 10.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 43.00% | 46.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 43.00% |
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 39.00% | 43.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Derivatives [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 4.00% | 3.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Liquidity Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 1.00% | 2.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 2.00% |
LG And E And KU Energy LLC [Member] | Other Postretirement Benefits Plan [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 116 | 98 | 88 | $ 116 | $ 98
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 116 | 98 | 88 |  |
Balance at end of period |  | 116 | 98 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | 15 | 20 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 14 |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2018 |  |  |  | 14 |
2019 |  |  |  | 15 |
2020 |  |  |  | 16 |
2021 |  |  |  | 16 |
2022 |  |  |  | 16 |
2023-2027 |  |  |  | 79 |
Expected Federal Subsidy (Details) [Abstract] |  |  |  |  |
Federal subsidy 2018 |  |  |  | 0 |
Federal subsidy 2019 |  |  |  | 0 |
Federal subsidy 2020 |  |  |  | 1 |
Federal subsidy 2021 |  |  |  | 0 |
Federal subsidy 2022 |  |  |  | 0 |
Federal subsidy 2023-2027 |  |  |  | 2 |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 325 | 318 | 297 | 325 | 318
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 325 | 318 | 297 |  |
Balance at end of period |  | 325 | 318 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 0 | $ 35 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 0 |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2018 |  |  |  | 26 |
2019 |  |  |  | 26 |
2020 |  |  |  | 26 |
2021 |  |  |  | 25 |
2022 |  |  |  | 24 |
2023-2027 |  |  |  | 104 |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Subsequent Event [Member] |  |  |  |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions | 54 |  |  |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] |  |  |  |  |
Information About Plan Assets (Numeric) [Abstract] |  |  |  |  |
Value of plan U.S. pension trust assets that relate to PPL subsidiary |  |  |  | 325 | $ 318
Undivided interest percentage in each asset category that PPL subsidiary holds |  | 9.00% | 10.00% |  |
Assumptions Used in Calculations (Numeric) [Abstract] |  |  |  |  |
The limited lives of four partnership of private equity investments (in years) |  | 10 years |  |  |
The amount of potential liability that maybe required to be funded by the master trust during life of the partnership |  |  |  | $ 28 |
Number Of Days Notice Required To Redeem Shares |  | 45 days |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 100.00% | 100.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 100.00% |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,561 | $ 3,381 | $ 3,381 | $ 3,561 | $ 3,381
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,561 | 3,381 |  |  |
Balance at end of period |  | 3,561 | 3,381 |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 716 | 714 | 714 | 716 | 714
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 716 | 714 |  |  |
Balance at end of period |  | 716 | 714 |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 931 | 909 | 909 | 931 | 909
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 931 | 909 |  |  |
Balance at end of period |  | 931 | 909 |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 37 | 40 | 42 | 37 | 40
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 37 | 40 | 42 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Purchases, sales and settlements |  | (4) | (3) |  |
Balance at end of period |  | 37 | 40 |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 301 | 181
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 301 | 181
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 229 | 152
Measured at fair value using net asset value per share |  |  |  | 364 | 272
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 229 | 152
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | International Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 538 | 551
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Commingled Debt Equity Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 611 | 546
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 186 | 381
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 186 | 381
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 883 | 850
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 870 | 837
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 13 | 13
Fair value at end of period |  |  | 10 |  |
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period |  |  | 10 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 0 | 0 |  |
Purchases, sales and settlements |  | 0 | 3 |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 10 | 8
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 10 | 8
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Real Estate Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 109 | 102
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Private Equity Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 80 | 80
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Hedge Fund Of Funds Alternative Investments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value using net asset value per share |  |  |  | 175 | 167
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 50 | 61
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 50 | 61
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 1 | 3
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 1 | 3
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 24 | 27
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 0 | 0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 3 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 24 | 27
Fair value at end of period |  |  | 32 |  |
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period |  |  | 32 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Purchases, sales and settlements |  | (4) | (6) |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Receivables And Payables Net [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 72 | (15) | (15) | 72 | (15)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 72 | (15) |  |  |
Balance at end of period |  | 72 | (15) |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Account 401 H [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | (145) | (123) | (123) | (145) | (123)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | (145) | (123) |  |  |
Balance at end of period |  | (145) | (123) |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Not Including 401 H Assets [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,488 | 3,243 | 3,243 | $ 3,488 | $ 3,243
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | $ 3,488 | 3,243 |  |  |
Balance at end of period |  | $ 3,488 | $ 3,243 |  |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 56.00% | 52.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 55.00% |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 32.00% | 30.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 14.00% | 12.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Alternative Investments [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 10.00% | 10.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 43.00% | 46.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 43.00% |
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 39.00% | 43.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Derivatives [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 4.00% | 3.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Liquidity Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 1.00% | 2.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 2.00% |

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