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Benefit Plans and Other Postretirement Benefits, Pension Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jan. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |  |  |  |
Defined Benefit Plan, Plan Assets, Payment for Settlement |  |  | $ 198 |  | $ 174 |  |
Components of Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |  |  |  |
Settlement Charge Recognized in Operating and Maintenance Expenses |  |  | 2,352 |  | 2,270 |  | $ 2,300
Significant Assumptions Used to Measure Costs [Abstract] |  |  |  |  |  |  |
Liability, Defined Benefit Plan, Noncurrent |  |  | 994 |  | 1,042 |  |
Pension Plan [Member] |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Accumulated Benefit Obligation at Dec. 31 |  |  | 3,275 |  | 3,612 |  |
Change in Projected Benefit Obligation [Roll Forward] |  |  |  |  |  |  |
Obligation at Jan. 1 | $ 3,477 |  | 3,828 |  | 3,682 |  |
Service cost |  |  | 94 |  | 94 |  | 92
Interest cost |  |  | 133 |  | 147 |  | 160
Plan amendments |  |  | 0 |  | (13) |  |
Actuarial loss |  |  | (224) |  | 259 |  |
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant |  |  | 0 |  | 0 |  |
Defined Benefit Plan, Benefit Obligation, Prescription Drug Subsidy Receipt |  |  | 0 |  | 0 |  |
Benefit payments |  |  | (354) |  | (341) |  |
Obligation at Dec. 31 |  |  | 3,477 |  | 3,828 |  | 3,682
Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |  |  |  |
Fair value of plan assets at Jan. 1 | 2,742 | [1] | 3,088 | [1] | 2,856 |  |
Actual return (loss) on plan assets |  |  | (142) |  | 411 |  |
Employer contributions |  |  | 150 |  | 162 |  |
Benefit payments |  |  | (354) |  | (341) |  |
Fair value of plan assets at Dec. 31 |  |  | 2,742 | [1] | 3,088 | [1] | 2,856
Funded Status of Plans at Dec. 31 [Abstract] |  |  |  |  |  |  |
Funded status |  |  | (735) |  | (740) |  |
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract] |  |  |  |  |  |  |
Net loss |  |  | 1,633 |  | 1,709 |  |
Prior service (credit) cost |  |  | (20) |  | (25) |  |
Total |  |  | 1,613 |  | 1,684 |  |
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract] |  |  |  |  |  |  |
Current regulatory assets |  |  | 94 |  | 100 |  |
Noncurrent regulatory assets |  |  | 1,446 |  | 1,511 |  |
Deferred income taxes |  |  | 19 |  | 19 |  |
Net-of-tax accumulated other comprehensive income |  |  | 54 |  | 54 |  |
Total |  |  | $ 1,613 |  | $ 1,684 |  |
Significant Assumptions Used to Measure Benefit Obligations [Abstract] |  |  |  |  |  |  |
Discount rate for year-end valuation (as a percent) |  |  | 4.31% |  | 3.63% |  |
Expected average long-term increase in compensation level (as a percent) |  |  | 3.75% |  | 3.75% |  |
Mortality table |  |  | RP-2014 |  | RP-2014 |  |
Cash Flows [Abstract] |  |  |  |  |  |  |
Total contributions to Xcel Energy's pension plans during the period |  |  | $ 150 |  | $ 162 |  | 125
Components of Net Periodic Benefit Cost (Credit) [Abstract] |  |  |  |  |  |  |
Service cost |  |  | 94 |  | 94 |  | 92
Interest cost |  |  | 133 |  | 147 |  | 160
Expected return on plan assets |  |  | (209) |  | (209) |  | (210)
Amortization of prior service cost (credit) |  |  | (5) |  | (2) |  | (2)
Amortization of net loss |  |  | 111 |  | 107 |  | 97
Settlement charge |  |  | 91 |  | 81 |  | 0
Net periodic benefit cost |  |  | 215 |  | 218 |  | 137
Costs not recognized due to regulation |  |  | (75) |  | (79) |  | (15)
Net benefit cost recognized for financial reporting |  |  | 140 |  | 139 |  | $ 122
Settlement Charge Recognized in Operating and Maintenance Expenses |  |  | $ 11 |  | $ 8 |  |
Significant Assumptions Used to Measure Costs [Abstract] |  |  |  |  |  |  |
Discount rate (as a percent) |  |  | 3.63% |  | 4.13% |  | 4.66%
Expected average long-term increase in compensation level (as a percent) |  |  | 3.75% |  | 3.75% |  | 4.00%
Expected average long-term rate of return on assets (as a percent) |  |  | 6.87% |  | 6.87% |  | 6.87%
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant |  |  | $ 0 |  | $ 0 |  |
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Liabilities |  |  | 0 |  | 0 |  |
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Liabilities |  |  | 0 |  | 0 |  |
Liability, Defined Benefit Plan, Current |  |  | 0 |  | 0 |  |
Liability, Defined Benefit Plan, Noncurrent |  |  | 735 |  | 740 |  |
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position |  |  | $ (735) |  | $ (740) |  |
Subsequent Event | Pension Plan [Member] |  |  |  |  |  |  |
Cash Flows [Abstract] |  |  |  |  |  |  |
Total contributions to Xcel Energy's pension plans during the period | $ 150 |  |  |  |  |  |
[1] | (a) See Note 10 for further information regarding fair value measurement inputs and methods.

X
- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i-k) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 + Details
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- Definition Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 + Details
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- Definition Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(6) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 + Details
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- Definition Amount of contributions received by defined benefit plan from participant which increase benefit obligation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount, before benefit payment, of receipt from prescription drug subsidy which increases benefit obligation of defined benefit postretirement plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 + Details
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- Definition Amount of contribution received by defined benefit plan from employer which increases plan assets. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 + Details
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