Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2017 USD ($) Plan	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 1,155	$ 1,104	$ 2,309	$ 2,208
Interest cost		1,555	1,704	3,109	3,408
Expected return on plan assets		(2,295)	(2,289)	(4,590)	(4,578)
Amortization of prior service cost (credit)		34	28	69	56
Amortization of net loss		1,461	1,348	2,923	2,696
Net benefit cost recognized for financial reporting		1,910	1,895	3,820	3,790
Total contributions to the pension plans during the period	$ 9,000
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		7	6	14	12
Interest cost		148	163	296	326
Expected return on plan assets		(8)	(6)	(16)	(12)
Amortization of prior service cost (credit)		(88)	(88)	(176)	(176)
Amortization of net loss		109	83	218	166
Net benefit cost recognized for financial reporting		$ 168	$ 158	$ 336	$ 316
Xcel Energy Inc. | Pension Benefits
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