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 (Credit) [Abstract]
Service cost		$ 2,751	$ 2,296	$ 5,503	$ 4,592
Interest cost		5,046	5,111	10,092	10,222
Expected return on plan assets		(7,152)	(6,545)	(14,305)	(13,090)
Amortization of prior service cost (credit)		10	13	20	27
Amortization of net loss (gain)		3,772	3,331	7,544	6,663
Net periodic benefit cost (credit)		4,427	4,206	8,854	8,414
Credits recognized (costs not recognized) due to the effects of regulation		686	708	1,399	1,415
Net benefit cost (credit) recognized for financial reporting		5,113	4,914	10,253	9,829
Total contributions to the pension plans during the period	$ 11,600
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		238	311	477	623
Interest cost		437	643	873	1,286
Expected return on plan assets		(635)	(811)	(1,270)	(1,623)
Amortization of prior service cost (credit)		(100)	(101)	(200)	(201)
Amortization of net loss (gain)		(160)	(81)	(320)	(161)
Net periodic benefit cost (credit)		(220)	(39)	(440)	(76)
Credits recognized (costs not recognized) due to the effects of regulation		0	0	0	0
Net benefit cost (credit) recognized for financial reporting		$ (220)	$ (39)	$ (440)	$ (76)
Xcel Energy Inc. | Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [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