Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2017 USD ($) Plan	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 23,547	$ 22,920
Interest cost		36,702	40,023
Expected return on plan assets		(52,317)	(52,575)
Amortization of prior service credit		(442)	(484)
Amortization of net loss		26,670	24,385
Net periodic benefit cost (credit)		34,160	34,269
Costs not recognized due to the effects of regulation		(4,015)	(4,452)
Net benefit cost (credit) recognized for financial reporting		30,145	29,817
Total contributions to Xcel Energy's pension plans during the period	$ 150,000
Number of pension plans to which contributions were made | Plan	4
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		465	432
Interest cost		5,984	6,527
Expected return on plan assets		(6,156)	(6,249)
Amortization of prior service credit		(2,671)	(2,672)
Amortization of net loss		1,672	1,011
Net periodic benefit cost (credit)		(706)	(951)
Costs not recognized due to the effects of regulation		0	0
Net benefit cost (credit) recognized for financial reporting		$ (706)	$ (951)