Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2016 USD ($) Plan	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 7,077	$ 7,889
Interest cost		11,358	10,804
Expected return on plan assets		(15,236)	(15,708)
Amortization of prior service cost (credit)		234	234
Amortization of net loss		9,194	11,548
Net periodic benefit cost		12,627	14,767
Costs not recognized due to the effects of regulation		(5,296)	(7,843)
Net benefit cost (credit) recognized for financial reporting		7,331	6,924
Total contributions to the pension plans during the period	$ 49,400
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		31	40
Interest cost		981	954
Expected return on plan assets		(43)	(30)
Amortization of prior service cost (credit)		(759)	(759)
Amortization of net loss		401	523
Net periodic benefit cost		611	728
Costs not recognized due to the effects of regulation		0	0
Net benefit cost (credit) recognized for financial reporting		$ 611	$ 728
Xcel Energy Inc. | Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Total contributions to the pension plans during the period	$ 125,000
Number of Xcel Energy's pension plans to which contributions were made | Plan	4