Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2017 USD ($) Plan	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Pension Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 1,154	$ 1,104	$ 3,463	$ 3,312
Interest cost		1,554	1,704	4,663	5,112
Expected return on plan assets		(2,295)	(2,289)	(6,885)	(6,867)
Amortization of prior service cost (credit)		35	28	104	84
Amortization of net loss		1,462	1,348	4,385	4,044
Net benefit cost recognized for financial reporting		1,910	1,895	5,730	5,685
Total contributions to the pension plans during the period	$ 9,000
Other Postretirement Benefits Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost		7	6	21	18
Interest cost		147	163	443	489
Expected return on plan assets		(7)	(6)	(23)	(18)
Amortization of prior service cost (credit)		(88)	(88)	(264)	(264)
Amortization of net loss		109	83	327	249
Net benefit cost recognized for financial reporting		$ 168	$ 158	$ 504	$ 474
Xcel Energy Inc. | Pension Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Total contributions to the pension plans during the period	$ 150,000
Number of Xcel Energy's pension plans to which contributions were made | Plan	4