Benefit Plans and Other Postretirement Benefits, Postretirement Benefit Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2020
Change in Projected Benefit Obligation [Roll Forward]
Defined Benefit Plan, Plan Assets, Payment for Settlement	$ 20		$ 198
Funded Status of Plans at Dec. 31 [Abstract]
Noncurrent liabilities	(785)		(994)
Cash Flows [Abstract]
Total contributions to Xcel Energy's postretirement health care plans during the year	15		11		$ 20
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan amendments	1		0
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	3,477		3,828
Service cost	86		94		94
Interest cost	145		133		147
Actuarial loss	273		(224)
Plan participants' contributions	0		0
Medicare subsidy reimbursements	0		0
Benefit payments	(281)		(354)
Obligation at Dec. 31	3,701		3,477		3,828
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	2,742	[1]	3,088
Actual return (loss) on plan assets	568		(142)
Employer contributions	155		150
Participant contributions	0		0
Benefit payments	(281)		(354)
Fair value of plan assets at Dec. 31	3,184	[1]	2,742	[1]	3,088
Funded status	(517)		(735)
Funded Status of Plans at Dec. 31 [Abstract]
Current liabilities	0		0
Noncurrent liabilities	(517)		(735)
Net postretirement amounts recognized on consolidated balance sheets	(517)		(735)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]
Net loss	1,447		1,633
Prior service (credit) cost	(15)		(20)
Total	1,432		1,613
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	78		94
Noncurrent regulatory assets	1,285		1,446
Current regulatory liabilities	0		0
Noncurrent regulatory liabilities	0		0
Deferred income taxes	18		19
Net-of-tax accumulated other comprehensive income	51		54
Total	$ 1,432		$ 1,613
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)	3.49%		4.31%
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 86		$ 94		94
Interest cost	145		133		147
Expected return on plan assets	(203)		(209)		(209)
Amortization of prior service cost (credit)	(5)		(5)		(2)
Amortization of net loss	87		111		107
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	(6)		(91)		(81)
Net periodic benefit cost	$ 116		$ 215		$ 218
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)	4.31%		3.63%		4.13%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.75%		3.75%		3.75%
Expected average long-term rate of return on assets (as a percent)	6.87%		6.87%		6.87%
Defined Benefit Plan, Costs Not Recognized Due To Regulation	$ (1)		$ (75)		$ (79)
Net benefit cost recognized for financial reporting	115		140		139
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan amendments	0		0
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	542		621
Service cost	2		2		2
Interest cost	22		22		24
Actuarial loss	19		(62)
Plan participants' contributions	8		8
Medicare subsidy reimbursements	1		1
Benefit payments	(47)		(50)
Obligation at Dec. 31	547		542		621
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	417	[2]	461
Actual return (loss) on plan assets	56		(13)
Employer contributions	15		11
Participant contributions	8		8
Benefit payments	(47)		(50)
Fair value of plan assets at Dec. 31	449	[2]	417	[2]	461
Funded status	(98)		(125)
Funded Status of Plans at Dec. 31 [Abstract]
Assets for Plan Benefits, Defined Benefit Plan	21
Current liabilities	(6)		(7)
Noncurrent liabilities	(113)		(118)
Net postretirement amounts recognized on consolidated balance sheets	(98)		(125)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]
Net loss	95		116
Prior service (credit) cost	(23)		(33)
Total	72		83
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	0		0
Noncurrent regulatory assets	80		89
Current regulatory liabilities	(1)		(1)
Noncurrent regulatory liabilities	(12)		(10)
Deferred income taxes	1		1
Net-of-tax accumulated other comprehensive income	4		4
Total	$ 72		$ 83
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)	3.47%		4.32%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Pre-65	6.00%		6.50%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Post-65	5.10%		5.30%
Ultimate health care trend assumption rate (as a percent)	4.50%		4.50%
Period until ultimate trend rate is reached (in years)	3 years		4 years
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 2		$ 2		2
Interest cost	22		22		24
Expected return on plan assets	(21)		(26)		(25)
Amortization of prior service cost (credit)	(10)		(11)		(11)
Amortization of net loss	5		8		7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0		0		0
Net periodic benefit cost	$ (2)		$ (5)		$ (3)
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)	4.32%		3.62%		4.13%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	0.00%		0.00%		0.00%
Expected average long-term rate of return on assets (as a percent)	4.50%		5.30%		5.80%
Defined Benefit Plan, Costs Not Recognized Due To Regulation	$ 1		$ 2		$ 0
Net benefit cost recognized for financial reporting	$ (1)		$ (3)		$ (3)
Forecast
Cash Flows [Abstract]
Expected contribution to postretirement health care plans during 2018						$ 10

[1] ^(a)  See Note 10 for further information regarding fair value measurement inputs and methods.

[2] ^(a)  See Note 10 for further information on fair value measurement inputs and methods.