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, 2018		Dec. 31, 2017		Dec. 31, 2016
Change in Projected Benefit Obligation [Roll Forward]
Defined Benefit Plan, Plan Assets, Payment for Settlement	$ 198		$ 174
Funded Status of Plans at Dec. 31 [Abstract]
Noncurrent liabilities	(994)		(1,042)
Cash Flows [Abstract]
Total contributions to Xcel Energy's postretirement health care plans during the year	11		20		$ 18
Expected contribution to postretirement health care plans during 2018	11
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	621		603
Service cost	2		2		2
Interest cost	22		24		26
Medicare subsidy reimbursements	1		1
Plan participants' contributions	8		8
Actuarial loss	(62)		33
Benefit payments	(50)		(50)
Obligation at Dec. 31	542		621		603
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	461	[1]	442
Actual return (loss) on plan assets	(13)		41
Participant contributions	8		8
Employer contributions	11		20
Benefit payments	(50)		(50)
Fair value of plan assets at Dec. 31	417	[1]	461	[1]	442
Funded Status of Plans at Dec. 31 [Abstract]
Funded status	(125)		(160)
Current liabilities	(7)		(3)
Noncurrent liabilities	(118)		(157)
Net postretirement amounts recognized on consolidated balance sheets	(125)		(160)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]
Net loss	116		147
Prior service (credit) cost	(33)		(44)
Total	83		103
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	89		107
Current regulatory liabilities	(1)		(1)
Noncurrent regulatory liabilities	(10)		(10)
Deferred income taxes	1		2
Net-of-tax accumulated other comprehensive income	4		5
Total	$ 83		$ 103
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)	4.32%		3.62%
Mortality table	RP-2014		RP-2014
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Pre-65	6.50%		7.00%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Post-65	5.35%		5.50%
Ultimate health care trend assumption rate (as a percent)	4.50%		4.50%
Period until ultimate trend rate is reached (in years)	4		5
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 2		$ 2		2
Interest cost	22		24		26
Expected return on plan assets	(26)		(25)		(25)
Amortization of prior service cost (credit)	(11)		(11)		(11)
Amortization of net loss	8		7		4
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0		0		0
Net periodic benefit cost	$ (5)		$ (3)		$ (4)
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)	3.62%		4.13%		4.65%
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)	5.30%		5.80%		5.80%
Defined Benefit Plan, Costs Not Recognized Due To Regulation	$ (2)		$ 0		$ 0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (3)		$ (3)		$ (4)

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