Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2016 USD ($) Plan	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 2,440	$ 2,751	$ 4,880	$ 5,503
Interest cost		5,315	5,046	10,630	10,092
Expected return on plan assets		(6,901)	(7,152)	(13,802)	(14,305)
Amortization of prior service cost (credit)		0	10	0	20
Amortization of net loss (gain)		2,997	3,772	5,994	7,544
Net periodic benefit cost (credit)		3,851	4,427	7,702	8,854
Defined Benefit Plan Credits Recognized Due To Effects of Regulation		638	686	716	1,399
Net benefit cost (credit) recognized for financial reporting		4,489	5,113	8,418	10,253
Total contributions to the pension plans during the period	$ 18,000
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		194	238	388	477
Interest cost		455	437	910	873
Expected return on plan assets		(594)	(635)	(1,188)	(1,270)
Amortization of prior service cost (credit)		(100)	(100)	(200)	(200)
Amortization of net loss (gain)		(146)	(160)	(292)	(320)
Net periodic benefit cost (credit)		(191)	(220)	(382)	(440)
Defined Benefit Plan Credits Recognized Due To Effects of Regulation		0	0	0	0
Net benefit cost (credit) recognized for financial reporting		$ (191)	$ (220)	$ (382)	$ (440)
Xcel Energy Inc. | Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [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