Benefit Plans and Other Postretirement Benefits, Postretirement Benefit Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Funded Status of Plans at Dec. 31 [Abstract]
Noncurrent liabilities	$ (1,112,366)	$ (941,002)
Postretirement Benefit Plan
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	584,267	642,869
Service cost	1,727	2,116	$ 3,457
Interest cost	26,107	25,297	34,028
Medicare subsidy reimbursements	2,058	1,958
Plan participants' contributions	6,896	6,718
Actuarial (gain) loss	32,954	(45,793)
Benefit payments	(50,925)	(48,898)
Obligation at Dec. 31	603,084	584,267	642,869
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	447,633	475,058
Actual return (loss) on plan assets	20,555	(3,570)
Plan participants' contributions	6,896	6,718
Employer contributions	17,946	18,325
Benefit payments	(50,925)	(48,898)
Fair value of plan assets at Dec. 31	442,105	447,633	475,058
Funded Status of Plans at Dec. 31 [Abstract]
Funded status	(160,979)	(136,634)
Noncurrent assets	437	1,820
Current liabilities	(6,395)	(7,495)
Noncurrent liabilities	(155,021)	(130,959)
Net postretirement amounts recognized on consolidated balance sheets	(160,979)	(136,634)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]
Net loss	136,391	103,039
Prior service (credit) cost	(54,239)	(64,925)
Total	82,152	38,114
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	247	352
Noncurrent regulatory assets	90,990	50,135
Current regulatory liabilities	(1,004)	(985)
Noncurrent regulatory liabilities	(14,221)	(16,916)
Deferred income taxes	2,387	2,148
Net-of-tax accumulated other comprehensive income	3,753	3,380
Total	$ 82,152	$ 38,114
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)	4.13%	4.65%
Mortality table	RP 2014	RP 2014
Health care costs trend rate - initial (as a percent)	5.50%	6.00%
Ultimate health care trend assumption rate (as a percent)	4.50%
Period until ultimate trend rate is reached (in years)	2 years
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]
One-percent increase in APBO	$ 57,329
One-percent decrease in APBO	(48,831)
One-percent increase in service and interest components	2,926
One-percent decrease in service and interest components	(2,477)
Cash Flows [Abstract]
Total contributions to Xcel Energy's postretirement health care plans during the year	17,900	$ 18,300	17,100
Expected contribution to postretirement health care plans during 2017	11,800
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1,727	2,116	3,457
Interest cost	26,107	25,297	34,028
Expected return on plan assets	(24,995)	(26,600)	(33,954)
Amortization of prior service cost (credit)	(10,686)	(10,686)	(10,688)
Amortization of net loss	4,042	5,404	11,740
Net periodic benefit cost	$ (3,805)	$ (4,469)	$ 4,583
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)	4.65%	4.08%	4.82%
Expected average long-term rate of return on assets (as a percent)	5.80%	5.80%	7.17%