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 (Credit) [Abstract]
Service cost		$ 7,065	$ 5,985	$ 21,195	$ 17,955
Interest cost		12,714	13,319	38,142	39,957
Expected return on plan assets		(18,147)	(17,677)	(54,442)	(53,031)
Amortization of prior service credit		(784)	(773)	(2,352)	(2,319)
Amortization of net loss		9,094	8,473	27,282	25,419
Net periodic benefit cost (credit)		9,942	9,327	29,825	27,981
Costs not recognized due to the effects of regulation		(366)	0	(1,098)	0
Net benefit cost (credit) recognized for financial reporting		9,576	9,327	28,727	27,981
Total contributions to the pension plans during the period	$ 20,000
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		232	479	696	1,436
Interest cost		4,375	5,926	13,124	17,778
Expected return on plan assets		(5,951)	(7,554)	(17,852)	(22,661)
Amortization of prior service credit		(1,562)	(1,562)	(4,686)	(4,685)
Amortization of net loss		618	1,609	1,856	4,826
Net periodic benefit cost (credit)		(2,288)	(1,102)	(6,862)	(3,306)
Costs not recognized due to the effects of regulation		0	0	0	0
Net benefit cost (credit) recognized for financial reporting		$ (2,288)	$ (1,102)	$ (6,862)	$ (3,306)
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