Share-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Share-Based Compensation Expense [Abstract]
Compensation cost for share-based awards	$ 45,006,000	[1],[2]	$ 35,807,000	[1],[2]	$ 29,672,000	[1],[2]
Tax benefit recognized in income	17,559,000		13,964,000		11,471,000
Total compensation cost capitalized	3,857,000		3,646,000		3,636,000
Matching contributions related to the Xcel Energy 401(k) plan included in compensation cost for share-based awards	21,600,000		20,700,000		19,300,000
Unrecognized compensation cost related to nonvested share-based compensation awards	15,400,000		18,600,000
Weighted-average period for recognition of unrecognized compensation cost related to nonvested share-based compensation awards (in years)	1.9
Stock Options [Member]
Stock Options Activity [Roll Forward]
Outstanding at Jan. 1 (in shares)	2,498,000		6,657,000		8,460,000
Exercisable at Jan. 1 (in shares)	2,498,000		6,657,000		8,460,000
Exercised (in shares)	(1,173,000)		(51,000)		(794,000)
Forfeited (in shares)	0		0		(11,000)
Expired (in shares)	(1,325,000)		(4,108,000)		(998,000)
Outstanding at Dec. 31 (in shares)	0		2,498,000		6,657,000
Exercisable at Dec. 31 (in shares)	0		2,498,000		6,657,000
Outstanding at Jan. 1, average exercise price (in dollars per share)	$ 30.42		$ 28.17		$ 27.05
Exercisable at Jan. 1, average exercise price (in dollars per share)	$ 30.42		$ 28.17		$ 27.05
Exercised, average exercise price (in dollars per share)	$ 25.90		$ 19.31		$ 19.84
Forfeited, average exercise price (in dollars per share)	$ 0		$ 0		$ 20.04
Expired, average exercise price (in dollars per share)	$ 34.42		$ 26.91		$ 25.40
Outstanding at Dec. 31, average exercise price (in dollars per share)	$ 0		$ 30.42		$ 28.17
Exercisable at Dec. 31, average exercise price (in dollars per share)	$ 0		$ 30.42		$ 28.17
Total Market Value and Total Intrinsic Value of Stock Options Exercised [Abstract]
Market value of exercises	30,761,000		1,087,000		16,429,000
Intrinsic value of options exercised	380,000	[3]	93,000	[3]	670,000	[3]
Cash received from stock options exercised	30,381,000		1,033,000		15,759,000
Tax benefit realized for the tax deductions from stock options exercised	157,000		40,000		277,000
Restricted Stock [Member]
Equity Instruments Other than Options Activity [Roll Forward]
Balance at January 1 (in shares)	55,000
Granted (in shares)	15,000		44,000		0
Vested (in shares)	(25,000)
Dividend equivalents (in shares)	2,000
Balance at December 31 (in shares)	47,000		55,000
Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract]
Balance at January 1, weighted average grant date fair value (in dollars per share)	$ 20.28
Granted, weighted average grant date fair value (in dollars per share)	$ 23.62		$ 20.47		$ 0
Vested, weighted average grant date fair value (in dollars per share)	$ 20.53
Dividend equivalents, weighted average grant date fair value (in dollars per share)	$ 24.37
Balance at December 31, weighted average grant date fair value (in dollars per share)	$ 21.36		$ 20.28
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Award vesting period (in years)	3Y
PSP Awards [Member]
Equity Instruments Other than Options Activity [Roll Forward]
Granted (in shares)	311,000		225,000		207,000
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Award vesting period (in years)	3Y
Minimum payout percentage (in hundredths)	0.00%
Maximum payout percentage (in hundredths)	200.00%
Amount of cash used to settle PSP awards	3,600,000		2,700,000
Awards settled (in shares)	305,000		267,000		293,000
Settlement amount (cash and common stock)	7,200,000		5,460,000		5,195,000
Restricted Stock Units (RSUs) [Member]
Equity Instruments Other than Options Activity [Roll Forward]
Balance at January 1 (in shares)	1,138,000
Granted (in shares)	828,000		601,000		597,000
Forfeited (in shares)	(270,000)
Vested (in shares)	(1,091,000)		(600,000)		(400,000)
Dividend equivalents (in shares)	68,000
Balance at December 31 (in shares)	673,000		1,138,000
Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract]
Balance at January 1, weighted average grant date fair value (in dollars per share)	$ 20.12
Granted, weighted average grant date fair value (in dollars per share)	$ 23.63		$ 21.26		$ 18.88
Forfeited, weighted average grant date fair value (in dollars per share)	$ 21.50
Vested, weighted average grant date fair value (in dollars per share)	$ 20.45
Dividend equivalents, weighted average grant date fair value (in dollars per share)	$ 21.18
Balance at December 31, weighted average grant date fair value (in dollars per share)	$ 23.46		$ 20.12
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Number of years after grant date in which RSUs issued in 2009 and 2010 will be forfeited if performance criteria has not been met (in years)	4Y
Number of years after grant date performance conditions for RSUs granted in 2011 will be measured (in years)	3Y
Number of performance criteria payout of RSUs and lapsing of restrictions on transfer of units are based	1
Total number of performance criteria used to evaluate payout of RSUs and lapsing of restrictions on transfer of units	2
Number of years after which restricted period for RSUs issued in 2011 whose performance conditions are based on EPS growth will lapse (in years)	3Y
Minimum percentage payout for RSUs issued in 2011 whose performance conditions are based on EPS growth (in hundredths)	0.00%
Maximum percentage payout for RSUs issued in 2011 whose performance conditions are based on EPS growth (in hundredths)	150.00%
Number of years after which restricted period for RSUs issued in 2011 whose performance conditions are based on environmental performance will lapse (in years)	3Y
Minimum percentage payout for RSUs issued in 2011 whose performance conditions are based on environmental performance (in hundredths)	0.00%
Maximum percentage payout for RSUs issued in 2011 whose performance conditions are based on environmental performance (in hundredths)	150.00%
Total fair value of nonvested RSUs	18,600,000
Weighted average remaining contractual life of nonvested RSUs (in years)	2.0Y
Total fair value of RSUs vested during the period	$ 30,100,000		$ 14,800,000		$ 800,000
Stock Equivalent Units [Member]
Equity Instruments Other than Options Activity [Roll Forward]
Balance at January 1 (in shares)	471,000
Granted (in shares)	60,000		66,000		72,000
Units distributed (in shares)	(29,000)
Dividend equivalents (in shares)	20,000
Balance at December 31 (in shares)	522,000		471,000
Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract]
Balance at January 1, weighted average grant date fair value (in dollars per share)	$ 19.90
Granted, weighted average grant date fair value (in dollars per share)	$ 25.12		$ 21.14		$ 17.87
Units distributed, weighted average grant date fair value (in dollars per share)	$ 20.31
Dividend equivalents, weighted average grant date fair value (in dollars per share)	$ 24.38
Balance at December 31, weighted average grant date fair value (in dollars per share)	$ 20.65		$ 19.90
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Number of shares of common stock into which the share-based compensation can be converted (in shares)	1
Xcel Energy Inc. Long-Term Incentive Plan [Member]
Share-Based Compensation Expense [Abstract]
Number of shares of common stock approved for issuance (in shares)	8,300,000
Xcel Energy Inc. Executive Annual Incentive Award Plan [Member]
Share-Based Compensation Expense [Abstract]
Number of shares of common stock approved for issuance (in shares)	1,200,000

[1] Compensation costs for share-based payment arrangements is included in other O&M expense in the consolidated statements of income.

[2] Included in compensation cost for share-based awards are matching contributions related to the Xcel Energy 401(k) plan, which totaled $21.6 million, $20.7 million and $19.3 million for the years ended 2011, 2010 and 2009, respectively.

[3] Intrinsic value is calculated as market price at exercise date less the option exercise price.