Benefit Plans and Other Postretirement Benefits (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2016 USD ($) Plan	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 6,487	$ 7,065	$ 19,445	$ 21,195
Interest cost		13,852	12,714	41,554	38,142
Expected return on plan assets		(17,692)	(18,147)	(53,076)	(54,442)
Amortization of prior service credit		(801)	(784)	(2,408)	(2,352)
Amortization of net loss		6,692	9,094	20,078	27,282
Net periodic benefit cost (credit)		8,538	9,942	25,593	29,825
Credits (costs) not recognized due to the effects of regulation		682	(366)	1,947	(1,098)
Net benefit cost (credit) recognized for financial reporting		9,220	9,576	27,540	28,727
Total contributions to the pension plans during the period	$ 16,800
Postretirement Health Care Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		192	232	576	696
Interest cost		4,518	4,375	13,554	13,124
Expected return on plan assets		(5,575)	(5,951)	(16,725)	(17,852)
Amortization of prior service credit		(1,562)	(1,562)	(4,686)	(4,686)
Amortization of net loss		483	618	1,449	1,856
Net periodic benefit cost (credit)		(1,944)	(2,288)	(5,832)	(6,862)
Credits (costs) not recognized due to the effects of regulation		0	0	0	0
Net benefit cost (credit) recognized for financial reporting		$ (1,944)	$ (2,288)	$ (5,832)	$ (6,862)
Xcel Energy Inc. | Pension Benefits
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Total contributions to the pension plans during the period	$ 125,000
Number of Xcel Energy's pension plans to which contributions were made | Plan	4