Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2015 USD ($) Plan	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 1,190	$ 1,132	$ 2,380	$ 2,264
Interest cost		1,630	1,814	3,260	3,628
Expected return on plan assets		(2,371)	(2,410)	(4,742)	(4,821)
Amortization of prior service cost (credit)		28	28	56	56
Amortization of net loss		1,701	1,654	3,402	3,308
Net benefit cost recognized for financial reporting		2,178	2,218	4,356	4,435
Total contributions to the pension plans during the period	$ 4,900
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		7	8	14	17
Interest cost		163	197	326	395
Expected return on plan assets		(7)	(13)	(15)	(26)
Amortization of prior service cost (credit)		(88)	(87)	(176)	(175)
Amortization of net loss		114	166	228	333
Net benefit cost recognized for financial reporting		$ 189	$ 271	$ 377	$ 544
Xcel Energy Inc. | Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Total contributions to the pension plans during the period	$ 90,000
Number of Xcel Energy's pension plans to which contributions were made | Plan	4