Benefit Plans and Other Postretirement Benefits (Details) (USD $)	1 Months Ended	3 Months Ended
	Jan. 31, 2012	Mar. 31, 2012	Mar. 31, 2011
Pension Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 21,329,000	$ 18,112,000
Interest cost		38,723,000	39,915,000
Expected return on plan assets		(51,476,000)	(55,286,000)
Amortization of prior service cost (credit)		5,266,000	5,633,000
Amortization of net loss		26,318,000	18,729,000
Net periodic benefit cost		40,160,000	27,103,000
Costs not recognized and additional cost recognized due to effects of regulation		(9,133,000)	(7,885,000)
Net benefit cost recognized for financial reporting		31,027,000	19,218,000
Total contributions to Xcel Energy's pension plans during the period	190,500,000
Number of pension plans to which contributions were made	4
Postretirement Health Care Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost		1,180,000	1,315,000
Interest cost		9,380,000	10,551,000
Expected return on plan assets		(7,111,000)	(7,968,000)
Amortization of transition obligation		3,580,000	3,611,000
Amortization of prior service cost (credit)		(1,888,000)	(1,233,000)
Amortization of net loss		3,965,000	3,343,000
Net periodic benefit cost		9,106,000	9,619,000
Costs not recognized and additional cost recognized due to effects of regulation		973,000	973,000
Net benefit cost recognized for financial reporting		$ 10,079,000	$ 10,592,000