CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) (USD $)									12 Months Ended
	Dec. 31, 2011 Common Stock [Member]	Dec. 31, 2010 Common Stock [Member]	Dec. 31, 2010 Preferred Stock $3.60 Series [Member]	Dec. 31, 2010 Preferred Stock $4.08 Series [Member]	Dec. 31, 2010 Preferred Stock $4.10 Series [Member]	Dec. 31, 2010 Preferred Stock $4.11 Series [Member]	Dec. 31, 2010 Preferred Stock $4.16 Series [Member]	Dec. 31, 2010 Preferred Stock $4.56 Series [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due Aug. 28, 2012 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due Aug. 15, 2015 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due March 1, 2018 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due March 1, 2019 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due Sept. 1, 2019 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due July 1, 2025 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due March 1, 2028 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due April 1, 2030 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due July 15, 2035 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due June 1, 2036 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due July 1, 2037 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due Nov. 1, 2039 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] First Mortgage Bonds [Member] Series Due Aug. 15, 2040 [Member]	Dec. 31, 2011 NSP-Minnesota [Member] Other [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due Oct. 1, 2012 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due March 1, 2013 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due April 1, 2014 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due Sept. 1, 2017 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due Aug. 1, 2018 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due Jan. 1, 2019 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due June 1, 2019 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due Nov. 15, 2020 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due Sept. 1, 2037 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due Aug. 1, 2038 [Member]	Dec. 31, 2011 PSCo [Member] First Mortgage Bonds [Member] Series Due Aug. 15, 2041 [Member]	Dec. 31, 2011 PSCo [Member] Capital Lease Obligations [Member]	Dec. 31, 2011 SPS [Member] First Mortgage Bonds [Member] Series Due Aug. 15, 2041 [Member]	Dec. 31, 2011 SPS [Member] Unsecured Senior Notes [Member] Senior E Due Oct. 1, 2016 [Member]	Dec. 31, 2011 SPS [Member] Unsecured Senior Notes [Member] Senior G Due Dec. 1, 2018 [Member]	Dec. 31, 2011 SPS [Member] Unsecured Senior Notes [Member] Senior C and D Due Oct. 1, 2033 [Member]	Dec. 31, 2011 SPS [Member] Unsecured Senior Notes [Member] Senior F Due Oct. 1, 2036 [Member]	Dec. 31, 2011 SPS [Member] Pollution Control Obligations, Securing Pollution Control Revenue Bonds [Member] Due July 1, 2011 [Member]	Dec. 31, 2011 SPS [Member] Pollution Control Obligations, Securing Pollution Control Revenue Bonds [Member] Due Sept. 1, 2016 [Member]	Dec. 31, 2011 NSP-Wisconsin [Member] First Mortgage Bonds [Member] Series Due Oct. 1, 2018 [Member]	Dec. 31, 2011 NSP-Wisconsin [Member] First Mortgage Bonds [Member] Series Due Sept. 1, 2038 [Member]	Dec. 31, 2011 NSP-Wisconsin [Member] City of La Crosse Resource Recovery Bond [Member] Series Due Nov. 1, 2021 [Member]	Dec. 31, 2011 NSP-Wisconsin [Member] Fort McCoy System Acquisition [Member] Due Oct. 15, 2030 [Member]	Dec. 31, 2011 NSP-Wisconsin [Member] Other [Member]	Dec. 31, 2011 Other Subsidiaries [Member] Various Eloigne Co. Affordable Housing Project Notes [Member] Due 2012-2045 [Member]	Dec. 31, 2011 Xcel Energy Inc. [Member] Unsecured Senior Notes [Member] Series Due April 1, 2017 [Member]	Dec. 31, 2011 Xcel Energy Inc. [Member] Unsecured Senior Notes [Member] Series Due May 15, 2020 [Member]	Dec. 31, 2011 Xcel Energy Inc. [Member] Unsecured Senior Notes [Member] Series Due July 1, 2036 [Member]	Dec. 31, 2011 Xcel Energy Inc. [Member] Unsecured Senior Notes [Member] Series Due Sept. 15, 2041 [Member]	Dec. 31, 2011 Xcel Energy Inc. [Member] Junior Subordinated Notes [Member] Series Due Jan. 1, 2068 [Member]	Dec. 31, 2011 Xcel Energy Inc. [Member] Capital Lease Obligations [Member]
Long-Term Debt
Debt instrument, issuer									NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	NSP-Minnesota	PSCo	PSCo	PSCo	PSCo	PSCo	PSCo	PSCo	PSCo	PSCo	PSCo	PSCo	PSCo	SPS	SPS	SPS	SPS	SPS	SPS	SPS	NSP-Wisconsin	NSP-Wisconsin	NSP-Wisconsin	NSP-Wisconsin	NSP-Wisconsin	Other Subsidiaries	Xcel Energy Inc.	Xcel Energy Inc.	Xcel Energy Inc.	Xcel Energy Inc.	Xcel Energy Inc.	Xcel Energy Inc.
Debt instrument, interest rate stated percentage (in hundredths)									8.00%	1.95%	5.25%	8.50%	8.50%	7.125%	6.50%	8.50%	5.25%	6.25%	6.20%	5.35%	4.85%		7.875%	4.875%	5.50%	4.375%	5.80%	5.10%	5.125%	3.20%	6.25%	6.50%	4.75%		4.50%	5.60%	8.75%	6.00%	6.00%	5.20%	5.75%	5.25%	6.375%	6.00%	7.00%			5.613%	4.70%	6.50%	4.80%	7.60%
Debt instrument, interest rate stated percentage rate range, minimum (in hundredths)																																		11.20%													0.00%
Debt instrument, interest rate stated percentage rate range, maximum (in hundredths)																																		14.30%													9.00%
Debt instrument, maturity date									Aug. 28, 2012	Aug. 15, 2015	Mar. 01, 2018	Mar. 01, 2019	Sep. 01, 2019	Jul. 01, 2025	Mar. 01, 2028	Apr. 01, 2030	Jul. 15, 2035	Jun. 01, 2036	Jul. 01, 2037	Nov. 01, 2039	Aug. 15, 2040		Oct. 01, 2012	Mar. 01, 2013	Apr. 01, 2014	Sep. 01, 2017	Aug. 01, 2018	Jan. 01, 2019	Jun. 01, 2019	Nov. 15, 2020	Sep. 01, 2037	Aug. 01, 2038	Aug. 15, 2041		Aug. 15, 2041	Oct. 01, 2016	Dec. 01, 2018	Oct. 01, 2033	Oct. 01, 2036	Jul. 01, 2011	Sep. 01, 2016	Oct. 01, 2018	Sep. 01, 2038	Nov. 01, 2021	Oct. 15, 2030			Apr. 01, 2017	May 15, 2020	Jul. 01, 2036	Sep. 15, 2041	Jan. 01, 2068
Debt instrument, maturity date range, start																																															2012
Debt instrument, maturity date range, end																																		2060													2045
Preferred Stockholders' Equity
Preferred stock, par value (in dollars per share)			$ 100	$ 100	$ 100	$ 100	$ 100	$ 100
Preferred stock, shares outstanding (in shares)			275,000	150,000	175,000	200,000	99,800	150,000
Preferred stock, annual dividend rate (in dollars per share)			$ 3.60	$ 4.08	$ 4.10	$ 4.11	$ 4.16	$ 4.56
Common Stockholders' Equity
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares outstanding (in shares)	486,493,933	482,333,750