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		$ 22,920	$ 24,828
Interest cost		40,023	37,131
Expected return on plan assets		(52,575)	(53,473)
Amortization of prior service cost (credit)		(484)	(451)
Amortization of net loss		24,385	31,288
Net periodic benefit cost (credit)		34,269	39,323
Costs not recognized due to the effects of regulation		(4,452)	(7,496)
Net benefit cost (credit) recognized for financial reporting		29,817	31,827
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
Interest cost		6,527	6,324
Expected return on plan assets		(6,249)	(6,650)
Amortization of prior service cost (credit)		(2,672)	(2,672)
Amortization of net loss		1,011	1,351
Net periodic benefit cost (credit)		(951)	(1,118)
Costs not recognized due to the effects of regulation		0	0
Net benefit cost (credit) recognized for financial reporting		$ (951)	$ (1,118)