Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2015 USD ($) Plan	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 1,190	$ 1,132	$ 3,570	$ 3,396
Interest cost		1,630	1,814	4,890	5,442
Expected return on plan assets		(2,371)	(2,411)	(7,113)	(7,232)
Amortization of prior service cost (credit)		27	28	83	84
Amortization of net loss		1,701	1,654	5,103	4,962
Net benefit cost recognized for financial reporting		2,177	2,217	6,533	6,652
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	9	21	26
Interest cost		164	198	490	593
Expected return on plan assets		(8)	(13)	(23)	(39)
Amortization of prior service cost (credit)		(87)	(88)	(263)	(263)
Amortization of net loss		114	167	342	500
Net benefit cost recognized for financial reporting		$ 190	$ 273	$ 567	$ 817
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