Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2015 USD ($) Plan	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 2,752	$ 2,296	$ 8,255	$ 6,888
Interest cost		5,046	5,111	15,138	15,333
Expected return on plan assets		(7,153)	(6,545)	(21,458)	(19,635)
Amortization of prior service cost (credit)		9	14	29	41
Amortization of net loss (gain)		3,772	3,332	11,316	9,995
Net periodic benefit cost (credit)		4,426	4,208	13,280	12,622
Defined Benefit Plan Regulatory Adjustments		740	707	2,139	2,122
Net benefit cost (credit) recognized for financial reporting		5,166	4,915	15,419	14,744
Total contributions to the pension plans during the period	$ 11,600
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		239	312	716	935
Interest cost		436	643	1,309	1,929
Expected return on plan assets		(635)	(812)	(1,905)	(2,435)
Amortization of prior service cost (credit)		(101)	(100)	(301)	(301)
Amortization of net loss (gain)		(159)	(80)	(479)	(241)
Net periodic benefit cost (credit)		(220)	(37)	(660)	(113)
Defined Benefit Plan Regulatory Adjustments		0	0	0	0
Net benefit cost (credit) recognized for financial reporting		$ (220)	$ (37)	$ (660)	$ (113)
Xcel Energy Inc. | Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Total contributions to the pension plans during the period	$ 90,000
Number of Xcel Energy's pension plans to which contributions were made | Plan	4