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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, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017
Pension Plan [Member] | U.S. [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | $ 3,109 | $ 3,488 | $ 3,243 | $ 3,109 | $ 3,488
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,109 | 3,488 | 3,243 |  |
Balance at end of period |  | 3,109 | 3,488 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 153 | 65 |  |
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] |  |  |  |  |
2019 |  |  |  | 274 |
2020 |  |  |  | 266 |
2021 |  |  |  | 265 |
2022 |  |  |  | 265 |
2023 |  |  |  | 264 |
2024-2028 |  |  |  | 1,290 |
Pension Plan [Member] | U.S. [Member] | Subsequent Event [Member] |  |  |  |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions | 50 |  |  |  |
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 |  |  |  | $ 71 |
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 | 3,109 | $ 3,488 | 3,488 | $ 3,109 | $ 3,488
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,109 | 3,488 |  |  |
Balance at end of period |  | 3,109 | 3,488 |  |
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 | 591 | 716 | 716 | 591 | 716
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 591 | 716 |  |  |
Balance at end of period |  | 591 | 716 |  |
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 | 924 | 931 | 931 | 924 | 931
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 924 | 931 |  |  |
Balance at end of period |  | 924 | 931 |  |
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 | 46 | 37 | 40 | 46 | 37
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 46 | 37 | 40 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | (1) | 1 |  |
Actual return on plan assets relating to assets sold during the period |  | 3 |  |  |
Purchases, sales and settlements |  | 7 | (4) |  |
Balance at end of period |  | 46 | 37 |  |
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 |  |  |  | 220 | 301
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 |  |  |  | 220 | 301
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 using net asset value per share |  |  |  | 340 | 364
Measured at fair value not using net asset value per share |  |  |  | 159 | 229
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 |  |  |  | 159 | 229
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 |  |  |  | 466 | 538
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 |  |  |  | 543 | 611
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 |  |  |  | 212 | 186
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 |  |  |  | 212 | 186
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 |  |  |  | 899 | 883
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 |  |  |  | 874 | 870
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 |  |  |  | 25 | 13
Fair value at end of period | 25 | 13 | 13 | 25 | 13
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 25 | 13 | 13 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | (2) | 0 |  |
Actual return on plan assets relating to assets sold during the period |  | 3 |  |  |
Purchases, sales and settlements |  | 11 | 0 |  |
Balance at end of period |  | 25 | 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 |  |  |  | 17 | 10
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 |  |  |  | 17 | 10
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 |  |  |  | 90 | 109
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Prior to Adjustments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,240 | 3,561 | 3,561 | 3,240 | 3,561
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,240 | 3,561 |  |  |
Balance at end of period |  | 3,240 | 3,561 |  |
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 |  |  |  | 65 | 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 | 175
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Derivatives [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 33 | 51
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | 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] | 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 |  |  |  | 33 | 51
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | 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 |  |  |  | 21 | 24
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 |  |  |  | 21 | 24
Fair value at end of period | 21 | 24 | 27 | 21 | 24
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 21 | 24 | 27 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Actual return on plan assets relating to assets sold during the period |  | 0 |  |  |
Purchases, sales and settlements |  | (4) | (4) |  |
Balance at end of period |  | 21 | 24 |  |
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 | (2) | 72 | 72 | (2) | 72
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | (2) | 72 |  |  |
Balance at end of period |  | (2) | 72 |  |
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 | (129) | (145) | (145) | $ (129) | $ (145)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | (129) | (145) |  |  |
Balance at end of period |  | (129) | (145) |  |
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 55.00% | 56.00%
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 |  |  |  | 30.00% | 32.00%
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 |  |  |  | 15.00% | 14.00%
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% | 43.00%
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% | 39.00%
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% | 4.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Liquidity Portfolio [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 2.00% | 1.00%
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 | 7,801 | 8,490 | 7,211 | $ 7,801 | $ 8,490
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 7,801 | 8,490 | 7,211 |  |
Balance at end of period |  | 7,801 | 8,490 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 188 | 486 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 277 |
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] |  |  |  |  |
2019 |  |  |  | 337 |
2020 |  |  |  | 340 |
2021 |  |  |  | 344 |
2022 |  |  |  | 349 |
2023 |  |  |  | 352 |
2024-2028 |  |  |  | 1,781 |
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 | 147 | $ 216 | 216 | 147 | 216
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 147 | 216 |  |  |
Balance at end of period |  | 147 | 216 |  |
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 | 2,937 | 3,140 | 3,140 | 2,937 | 3,140
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 2,937 | 3,140 |  |  |
Balance at end of period |  | 2,937 | 3,140 |  |
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% | 2.00%
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 |  |  |  | $ 147 | $ 216
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 |  |  |  | 147 | 216
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 |  |  |  | 0.00% | 2.00%
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 |  |  |  | $ 27 | $ 157
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% | 1.00%
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 |  |  |  | $ 76 | $ 98
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% | 1.00%
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 |  |  |  | $ 49 | $ 60
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% | 1.00%
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 |  |  |  | $ 105 | $ 123
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% | 1.00%
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 |  |  |  | $ 44 | $ 62
Pension Plan [Member] | U.K. [Member] | Global Equities Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 19.00% | 16.00%
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 |  |  |  | $ 1,465 | $ 1,335
Pension Plan [Member] | U.K. [Member] | Global Tactical Asset Allocation Equity Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 31.00% | 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 |  |  |  | $ 2,437 | $ 2,807
Pension Plan [Member] | U.K. [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 38.00% | 37.00%
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 |  |  |  | $ 4 | $ 3
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 |  |  |  | 4 | 3
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 |  |  |  | 2,933 | 3,137
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 |  |  |  | 2,933 | 3,137
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 |  |  |  | $ 485 | $ 492
Pension Plan [Member] | U.K. [Member] | Total Trust Assets Prior to Adjustments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 7,772 | 8,490 | 8,490 | 7,772 | 8,490
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 7,772 | 8,490 |  |  |
Balance at end of period |  | 7,772 | 8,490 |  |
Pension Plan [Member] | U.K. [Member] | Receivables And Payables Net [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 29 | 0 | 0 | $ 29 | $ 0
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 29 | 0 |  |  |
Balance at end of period |  | 29 | 0 |  |
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 | 301 | 405 | 378 | $ 301 | $ 405
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 301 | 405 | 378 |  |
Balance at end of period |  | 301 | 405 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | 23 | 15 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 15 |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2019 |  |  |  | 50 |
2020 |  |  |  | 50 |
2021 |  |  |  | 49 |
2022 |  |  |  | 48 |
2023 |  |  |  | 46 |
2024-2028 |  |  |  | 210 |
Expected Federal Subsidy (Details) [Abstract] |  |  |  |  |
Federal subsidy 2019 |  |  |  | 0 |
Federal subsidy 2020 |  |  |  | 1 |
Federal subsidy 2021 |  |  |  | 0 |
Federal subsidy 2022 |  |  |  | 1 |
Federal subsidy 2023 |  |  |  | 0 |
Federal subsidy 2024-2028 |  |  |  | 1 |
Other Postretirement Benefits Plan [Member] | Level 1 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 6 | 10 | 10 | 6 | 10
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 6 | 10 |  |  |
Balance at end of period |  | 6 | 10 |  |
Other Postretirement Benefits Plan [Member] | Level 2 [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 28 | 30 | 30 | 28 | 30
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 28 | 30 |  |  |
Balance at end of period |  | 28 | 30 |  |
Other Postretirement Benefits Plan [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 |  |
Other Postretirement Benefits Plan [Member] | Cash And Cash Equivalents [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 4.00% | 4.00%
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 | 6 | $ 10 | 10 | $ 6 | $ 10
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 6 | 10 |  |  |
Balance at end of period |  | 6 | 10 |  |
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 |  |  |  | 6 | 10
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 |  |  |  | 40.00% | 47.00%
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 |  |  |  | $ 69 | $ 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 |  |  |  | $ 68 | $ 96
Other Postretirement Benefits Plan [Member] | Debt Securities [Member] |  |  |  |  |
Actual Allocation by Plan Asset (Details) [Abstract] |  |  |  |  |
Percentage of trust assets |  |  |  | 56.00% | 49.00%
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 | 28 | 30 | 30 | $ 28 | $ 30
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 28 | 30 |  |  |
Balance at end of period |  | 28 | 30 |  |
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 |  |  |  | 28 | 30
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] | Total Trust Assets Prior to Adjustments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 171 | 259 | 259 | 171 | 259
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 171 | 259 |  |  |
Balance at end of period |  | 171 | 259 |  |
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 | 129 | 145 | 145 | 129 | 145
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 129 | 145 |  |  |
Balance at end of period |  | 129 | 145 |  |
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 | 1,294 | 1,402 | 1,315 | 1,294 | 1,402
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 1,294 | 1,402 | 1,315 |  |
Balance at end of period |  | 1,294 | 1,402 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 109 | $ 21 |  |
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] |  |  |  |  |
2019 |  |  |  | 112 |
2020 |  |  |  | 112 |
2021 |  |  |  | 113 |
2022 |  |  |  | 113 |
2023 |  |  |  | 112 |
2024-2028 |  |  |  | 547 |
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 | 20 |  |  |  |
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 |  |  |  | 1,300 | $ 1,400
Undivided interest percentage in each asset category that PPL subsidiary holds |  | 42.00% | 40.00% |  |
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 |  |  |  | $ 71 |
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 | 3,240 | $ 3,561 | $ 3,561 | $ 3,240 | $ 3,561
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,240 | 3,561 |  |  |
Balance at end of period |  | 3,240 | 3,561 |  |
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 | 591 | 716 | 716 | 591 | 716
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 591 | 716 |  |  |
Balance at end of period |  | 591 | 716 |  |
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 | 924 | 931 | 931 | 924 | 931
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 924 | 931 |  |  |
Balance at end of period |  | 924 | 931 |  |
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 | 46 | 37 | 40 | 46 | 37
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 46 | 37 | 40 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | (1) | 1 |  |
Actual return on plan assets relating to assets sold during the period |  | 3 |  |  |
Purchases, sales and settlements |  | 7 | (4) |  |
Balance at end of period |  | 46 | 37 |  |
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 |  |  |  | 220 | 301
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 |  |  |  | 220 | 301
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 using net asset value per share |  |  |  | 340 | 364
Measured at fair value not using net asset value per share |  |  |  | 159 | 229
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 |  |  |  | 159 | 229
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 |  |  |  | 466 | 538
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 |  |  |  | 543 | 611
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 |  |  |  | 212 | 186
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 |  |  |  | 212 | 186
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 |  |  |  | 899 | 883
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 |  |  |  | 874 | 870
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 |  |  |  | 25 | 13
Fair value at end of period | 25 | 13 | 13 | 25 | 13
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 25 | 13 | 13 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | (2) | 0 |  |
Actual return on plan assets relating to assets sold during the period |  | 3 |  |  |
Purchases, sales and settlements |  | 11 | 0 |  |
Balance at end of period |  | 25 | 13 |  |
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 |  |  |  | 17 | 10
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 |  |  |  | 17 | 10
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 |  |  |  | 90 | 109
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Prior to Adjustments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,109 | 3,488 | 3,488 | 3,109 | 3,488
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,109 | 3,488 |  |  |
Balance at end of period |  | 3,109 | 3,488 |  |
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 |  |  |  | 65 | 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 | 175
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Derivatives [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 33 | 51
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | 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] | 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 |  |  |  | 33 | 51
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | 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 |  |  |  | 21 | 24
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 |  |  |  | 21 | 24
Fair value at end of period | 21 | 24 | 27 | 21 | 24
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 21 | 24 | 27 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Actual return on plan assets relating to assets sold during the period |  | 0 |  |  |
Purchases, sales and settlements |  | (4) | (4) |  |
Balance at end of period |  | 21 | 24 |  |
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 | (2) | 72 | 72 | (2) | 72
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | (2) | 72 |  |  |
Balance at end of period |  | (2) | 72 |  |
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 | (129) | (145) | (145) | $ (129) | $ (145)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | (129) | (145) |  |  |
Balance at end of period |  | (129) | (145) |  |
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 |  |  |  | 55.00% | 56.00%
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 |  |  |  | 30.00% | 32.00%
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 |  |  |  | 15.00% | 14.00%
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% | 43.00%
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% | 39.00%
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% | 4.00%
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 |  |  |  | 2.00% | 1.00%
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 | 117 | 116 | 98 | $ 117 | $ 116
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 117 | 116 | 98 |  |
Balance at end of period |  | 117 | 116 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | 24 | 15 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 15 |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2019 |  |  |  | 15 |
2020 |  |  |  | 15 |
2021 |  |  |  | 16 |
2022 |  |  |  | 16 |
2023 |  |  |  | 16 |
2024-2028 |  |  |  | 78 |
Expected Federal Subsidy (Details) [Abstract] |  |  |  |  |
Federal subsidy 2019 |  |  |  | 0 |
Federal subsidy 2020 |  |  |  | 0 |
Federal subsidy 2021 |  |  |  | 0 |
Federal subsidy 2022 |  |  |  | 1 |
Federal subsidy 2023 |  |  |  | 0 |
Federal subsidy 2024-2028 |  |  |  | 1 |
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 | 281 | 325 | 318 | 281 | 325
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 281 | 325 | 318 |  |
Balance at end of period |  | 281 | 325 |  |
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract] |  |  |  |  |
Employer contributions |  | $ 10 | $ 0 |  |
Amount to be contributed to plan in the next fiscal year |  |  |  | 0 |
Estimated Future Benefit Payments (Details) [Abstract] |  |  |  |  |
2019 |  |  |  | 25 |
2020 |  |  |  | 25 |
2021 |  |  |  | 24 |
2022 |  |  |  | 23 |
2023 |  |  |  | 22 |
2024-2028 |  |  |  | 95 |
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 | 1 |  |  |  |
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 |  |  |  | 281 | $ 325
Undivided interest percentage in each asset category that PPL subsidiary holds |  | 9.00% | 9.00% |  |
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 |  |  |  | $ 71 |
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 | 3,240 | $ 3,561 | $ 3,561 | $ 3,240 | $ 3,561
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,240 | 3,561 |  |  |
Balance at end of period |  | 3,240 | 3,561 |  |
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 | 591 | 716 | 716 | 591 | 716
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 591 | 716 |  |  |
Balance at end of period |  | 591 | 716 |  |
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 | 924 | 931 | 931 | 924 | 931
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 924 | 931 |  |  |
Balance at end of period |  | 924 | 931 |  |
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 | 46 | 37 | 40 | 46 | 37
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 46 | 37 | 40 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | (1) | 1 |  |
Actual return on plan assets relating to assets sold during the period |  | 3 |  |  |
Purchases, sales and settlements |  | 7 | (4) |  |
Balance at end of period |  | 46 | 37 |  |
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 |  |  |  | 220 | 301
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 |  |  |  | 220 | 301
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 using net asset value per share |  |  |  | 340 | 364
Measured at fair value not using net asset value per share |  |  |  | 159 | 229
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 |  |  |  | 159 | 229
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 |  |  |  | 466 | 538
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 |  |  |  | 543 | 611
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 |  |  |  | 212 | 186
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 |  |  |  | 212 | 186
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 |  |  |  | 899 | 883
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 |  |  |  | 874 | 870
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 |  |  |  | 25 | 13
Fair value at end of period | 25 | 13 | 13 | 25 | 13
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 25 | 13 | 13 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | (2) | 0 |  |
Actual return on plan assets relating to assets sold during the period |  | 3 |  |  |
Purchases, sales and settlements |  | 11 | 0 |  |
Balance at end of period |  | 25 | 13 |  |
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 |  |  |  | 17 | 10
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 |  |  |  | 17 | 10
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 |  |  |  | 90 | 109
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Prior to Adjustments [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Fair value at end of period | 3,109 | 3,488 | 3,488 | 3,109 | 3,488
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 3,109 | 3,488 |  |  |
Balance at end of period |  | 3,109 | 3,488 |  |
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 |  |  |  | 65 | 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 | 175
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Derivatives [Member] |  |  |  |  |
Defined benefit plan fair value of plan assets (Details) [Abstract] |  |  |  |  |
Measured at fair value not using net asset value per share |  |  |  | 33 | 51
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | 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] | 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 |  |  |  | 33 | 51
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | 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 |  |  |  | 21 | 24
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 |  |  |  | 21 | 24
Fair value at end of period | 21 | 24 | 27 | 21 | 24
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | 21 | 24 | 27 |  |
Actual return on plan assets relating to assets still held at the reporting date |  | 1 | 1 |  |
Actual return on plan assets relating to assets sold during the period |  | 0 |  |  |
Purchases, sales and settlements |  | (4) | (4) |  |
Balance at end of period |  | 21 | 24 |  |
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 | (2) | 72 | 72 | (2) | 72
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | (2) | 72 |  |  |
Balance at end of period |  | (2) | 72 |  |
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 | (129) | (145) | (145) | $ (129) | $ (145)
Change in Fair Value of Level 3 Plan Assets [Roll Forward] |  |  |  |  |
Balance at beginning of period | $ (129) | (145) |  |  |
Balance at end of period |  | $ (129) | $ (145) |  |
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 |  |  |  | 55.00% | 56.00%
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 |  |  |  | 30.00% | 32.00%
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 |  |  |  | 15.00% | 14.00%
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% | 43.00%
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% | 39.00%
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% | 4.00%
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 |  |  |  | 2.00% | 1.00%
Target Allocations (Details ) [Abstract] |  |  |  |  |
Target asset allocation |  |  |  | 2.00% |

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