Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2016 USD ($) Plan	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 22,940	$ 24,828	$ 68,805	$ 74,484
Interest cost		40,027	37,131	120,078	111,393
Expected return on plan assets		(52,575)	(53,473)	(157,725)	(160,418)
Amortization of prior service credit		(478)	(451)	(1,439)	(1,353)
Amortization of net loss		24,384	31,288	73,154	93,864
Net periodic benefit cost (credit)		34,298	39,323	102,873	117,970
Costs not recognized due to the effects of regulation		(3,976)	(7,016)	(12,587)	(22,035)
Net benefit cost (credit) recognized for financial reporting		30,322	32,307	90,286	95,935
Total contributions to Xcel Energy's pension plans during the period	$ 125,000
Number of pension plans to which contributions were made | Plan	4
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		432	529	1,295	1,587
Interest cost		6,527	6,324	19,580	18,972
Expected return on plan assets		(6,249)	(6,650)	(18,746)	(19,950)
Amortization of prior service credit		(2,672)	(2,672)	(8,015)	(8,015)
Amortization of net loss		1,011	1,351	3,031	4,053
Net periodic benefit cost (credit)		(951)	(1,118)	(2,855)	(3,353)
Costs not recognized due to the effects of regulation		0	0	0	0
Net benefit cost (credit) recognized for financial reporting		$ (951)	$ (1,118)	$ (2,855)	$ (3,353)