Benefit Plans and Other Postretirement Benefits, Postretirement Benefit Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2019
Cash Flows [Abstract]
Total contributions to Xcel Energy's postretirement health care plans during the year	$ 5,000,000	$ 5,000,000	$ 5,000,000
Significant Assumptions Used to Measure Costs [Abstract]
Liability, Defined Benefit Plan, Noncurrent	(275,300,000)	(287,800,000)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at net asset value	35,800,000	0
Plan amendments	0	0
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	429,200,000	421,800,000
Service cost	700,000	700,000	800,000
Interest cost	15,000,000	16,800,000	18,100,000
Medicare subsidy reimbursements	900,000	1,000,000
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	6,500,000	6,000,000
Actuarial (gain) loss	(40,600,000)	18,300,000
Benefit payments	(35,200,000)	(35,400,000)
Obligation at Dec. 31	376,500,000	429,200,000	421,800,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	406,400,000	393,500,000
Actual return (loss) on plan assets	(11,100,000)	37,000,000
Plan participants' contributions	6,500,000	6,000,000
Employer contributions	5,500,000	5,300,000
Benefit payments	(35,200,000)	(35,400,000)
Fair value of plan assets at Dec. 31	372,100,000	406,400,000	393,500,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status	(4,400,000)	(22,800,000)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]
Net loss	66,900,000	77,800,000
Prior service (credit) cost	15,300,000	21,500,000
Total	51,600,000	56,300,000
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Noncurrent regulatory assets	$ 51,600,000	$ 56,300,000
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Pre-65	6.50%	7.00%
Ultimate health care trend assumption rate (as a percent)	4.50%	4.50%
Period until ultimate trend rate is reached (in years)	4	5
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Post-65	5.30%	5.50%
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 700,000	$ 700,000	800,000
Interest cost	15,000,000	16,800,000	18,100,000
Expected return on plan assets	(22,700,000)	(21,900,000)	(22,300,000)
Amortization of prior service (credit) cost	(6,200,000)	(6,200,000)	(6,300,000)
Amortization of net loss	4,000,000	3,800,000	1,900,000
Net periodic pension cost	$ (9,200,000)	$ (6,800,000)	$ (7,800,000)
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)	3.62%	4.13%	4.65%
Expected average long-term rate of return on assets (as a percent)	5.80%	5.80%	5.80%
Liability, Defined Benefit Plan, Noncurrent	$ (4,400,000)	$ (22,800,000)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	$ (4,400,000)	$ (22,800,000)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.32%	3.62%
Mortality table	RP-2014	RP-2014
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Assets		$ 0
Deferred Income Taxes	0	0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Net-Of-Tax Accumulated Other Comprehensive Income	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	$ 0
Defined Benefit Plan, Costs Not Recognized Due To Regulation	1,800,000	0	0
Net benefit cost recognized for financial reporting	(7,400,000)	(6,800,000)	(7,800,000)
Xcel Energy Inc.
Cash Flows [Abstract]
Total contributions to Xcel Energy's postretirement health care plans during the year	$ 11,000,000	$ 20,000,000	$ 18,000,000
Subsequent Event
Cash Flows [Abstract]
Expected contribution to postretirement health care plans during 2018				$ 0
Subsequent Event | Xcel Energy Inc.
Cash Flows [Abstract]
Expected contribution to postretirement health care plans during 2018				$ 11,000,000