Schedule I Condensed Financial Statements of Xcel Energy Inc. (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income
Equity earnings of subsidiaries									$ 30,527,000	$ 29,948,000	$ 24,664,000
Expenses and other deductions
Other income									(9,255,000)	(31,143,000)	(9,771,000)
Interest charges and financing costs									591,098,000	577,291,000	561,654,000
Income from continuing operations before income taxes									1,309,690,000	1,188,591,000	1,056,838,000
Income tax benefit									468,316,000	436,635,000	371,314,000
Income from continuing operations	140,941,000	338,295,000	158,671,000	203,467,000	136,503,000	312,488,000	135,625,000	167,340,000	841,374,000	751,956,000	685,524,000
Income (loss) from discontinued operations, net of tax	(432,000)	37,000	91,000	102,000	131,000	(182,000)	4,151,000	(222,000)	(202,000)	3,878,000	(4,637,000)
Net income	140,509,000	338,332,000	158,762,000	203,569,000	136,634,000	312,306,000	139,776,000	167,118,000	841,172,000	755,834,000	680,887,000
Dividend requirements on preferred stock									3,534,000	4,241,000	4,241,000
Premium on redemption of preferred stock									3,260,000	0	0
Earnings available to common shareholders	140,509,000	333,658,000	157,702,000	202,509,000	135,573,000	311,246,000	138,716,000	166,058,000	834,378,000	751,593,000	676,646,000
Weighted average common shares outstanding:
Basic (in shares)									485,039	462,052	456,433
Diluted (in shares)									485,615	463,391	457,139
Earnings per average common share - basic:
Income from continuing operations (in dollars per share)									$ 1.72	$ 1.62	$ 1.49
Income (loss) from discontinued operations (in dollars per share)									$ 0	$ 0.01	$ (0.01)
Earnings per share (in dollars per share)	$ 0.29	$ 0.69	$ 0.33	$ 0.42	$ 0.29	$ 0.68	$ 0.30	$ 0.36	$ 1.72	$ 1.63	$ 1.48
Earnings per average common share - diluted:
Income from continuing operations (in dollars per share)									$ 1.72	$ 1.61	$ 1.49
Income (loss) from discontinued operations (in dollars per share)									$ 0	$ 0.01	$ (0.01)
Earnings per share (in dollars per share)	$ 0.29	$ 0.69	$ 0.33	$ 0.42	$ 0.29	$ 0.67	$ 0.30	$ 0.36	$ 1.72	$ 1.62	$ 1.48
Cash dividends declared per common share (in dollars per share)	$ 0.26	$ 0.26	$ 0.26	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 1.03	$ 1.00	$ 0.97
Operating activities
Net cash provided by operating activities									2,405,522,000	1,893,942,000	1,912,906,000
Investing activities
Net cash used in investing activities									(2,247,801,000)	(2,806,724,000)	(1,734,680,000)
Financing activities
Proceeds from (repayment of) short-term borrowings, net									(247,400,000)	7,400,000	3,750,000
Proceeds from issuance of long-term debt									688,598,000	1,433,406,000	689,915,000
Repayment of long-term debt									(105,623,000)	(560,383,000)	(621,296,000)
Proceeds from issuance of common stock									38,691,000	457,258,000	20,133,000
Redemption of preferred stock									(104,980,000)	0	0
Dividends paid									(474,760,000)	(432,110,000)	(414,922,000)
Net cash (used in) provided by financing activities									(205,474,000)	905,571,000	(322,420,000)
Net change in cash and cash equivalents									(47,753,000)	(7,211,000)	(144,194,000)
Cash and cash equivalents at beginning of period				108,437,000				115,648,000	108,437,000	115,648,000	259,842,000
Cash and cash equivalents at end of period	60,684,000				108,437,000				60,684,000	108,437,000	115,648,000
Assets
Cash and cash equivalents	60,684,000				108,437,000				60,684,000	108,437,000	115,648,000
Total current assets	2,982,564,000				2,732,643,000				2,982,564,000	2,732,643,000
Investment in subsidiaries	92,700,000				97,600,000				92,700,000	97,600,000
Other assets	155,926,000				180,044,000				155,926,000	180,044,000
Total other assets	4,161,336,000				3,991,965,000				4,161,336,000	3,991,965,000
Total assets	29,497,267,000				27,387,690,000				29,497,267,000	27,387,690,000
Liabilities and Equity
Dividends payable	126,487,000				122,847,000				126,487,000	122,847,000
Short-term debt	219,000,000				466,400,000				219,000,000	466,400,000	459,000,000
Other current liabilities	381,819,000				276,111,000				381,819,000	276,111,000
Total current liabilities	3,588,639,000				2,536,533,000				3,588,639,000	2,536,533,000
Other liabilities	203,313,000				249,635,000				203,313,000	249,635,000
Commitments and contingent liabilities
Capitalization
Preferred stockholders' equity	0				104,980,000				0	104,980,000
Common stockholders' equity	8,482,198,000				8,083,519,000				8,482,198,000	8,083,519,000
Total liabilities and equity	29,497,267,000				27,387,690,000				29,497,267,000	27,387,690,000
Xcel Energy Inc. [Member]
Income
Equity earnings of subsidiaries									904,315,000	818,212,000	743,798,000
Total income									904,315,000	818,212,000	743,798,000
Expenses and other deductions
Operating expenses									14,513,000	11,849,000	9,116,000
Other income									(760,000)	(681,000)	(1,295,000)
Interest charges and financing costs									104,297,000	112,510,000	101,118,000
Total expenses and other deductions									118,050,000	123,678,000	108,939,000
Income from continuing operations before income taxes									786,265,000	694,534,000	634,859,000
Income tax benefit									(55,109,000)	(57,422,000)	(50,665,000)
Income from continuing operations									841,374,000	751,956,000	685,524,000
Income (loss) from discontinued operations, net of tax									(202,000)	3,878,000	(4,637,000)
Net income									841,172,000	755,834,000	680,887,000
Dividend requirements on preferred stock									3,534,000	4,241,000	4,241,000
Premium on redemption of preferred stock									3,260,000	0	0
Earnings available to common shareholders									834,378,000	751,593,000	676,646,000
Weighted average common shares outstanding:
Basic (in shares)									485,039	462,052	456,433
Diluted (in shares)									485,615	463,391	457,139
Earnings per average common share - basic:
Income from continuing operations (in dollars per share)									$ 1.72	$ 1.62	$ 1.49
Income (loss) from discontinued operations (in dollars per share)									$ 0	$ 0.01	$ (0.01)
Earnings per share (in dollars per share)									$ 1.72	$ 1.63	$ 1.48
Earnings per average common share - diluted:
Income from continuing operations (in dollars per share)									$ 1.72	$ 1.61	$ 1.49
Income (loss) from discontinued operations (in dollars per share)									$ 0	$ 0.01	$ (0.01)
Earnings per share (in dollars per share)									$ 1.72	$ 1.62	$ 1.48
Cash dividends declared per common share (in dollars per share)									$ 1.03	$ 1.00	$ 0.97
Operating activities
Net cash provided by operating activities									595,732,000	537,840,000	627,013,000
Investing activities
Capital contributions to subsidiaries									(287,495,000)	(523,369,000)	(297,004,000)
Net cash used in investing activities									(287,495,000)	(523,369,000)	(297,004,000)
Financing activities
Proceeds from (repayment of) short-term borrowings, net									(21,000,000)	(216,000,000)	13,750,000
Proceeds from issuance of long-term debt									246,877,000	543,923,000	0
Repayment of long-term debt									0	(358,636,000)	0
Proceeds from issuance of common stock									38,691,000	457,258,000	20,133,000
Redemption of preferred stock									(104,980,000)	0	0
Dividends paid									(474,760,000)	(432,110,000)	(414,922,000)
Net cash (used in) provided by financing activities									(315,172,000)	(5,565,000)	(381,039,000)
Net change in cash and cash equivalents									(6,935,000)	8,906,000	(51,030,000)
Cash and cash equivalents at beginning of period				9,654,000				748,000	9,654,000	748,000	51,778,000
Cash and cash equivalents at end of period	2,719,000				9,654,000				2,719,000	9,654,000	748,000
Assets
Cash and cash equivalents	2,719,000				9,654,000				2,719,000	9,654,000	748,000
Accounts receivable from subsidiaries	271,895,000				266,323,000				271,895,000	266,323,000
Other current assets	28,399,000				35,276,000				28,399,000	35,276,000
Total current assets	303,013,000				311,253,000				303,013,000	311,253,000
Investment in subsidiaries	10,089,116,000				9,559,780,000				10,089,116,000	9,559,780,000
Other assets	154,353,000				134,157,000				154,353,000	134,157,000
Total other assets	10,243,469,000				9,693,937,000				10,243,469,000	9,693,937,000
Total assets	10,546,482,000				10,005,190,000				10,546,482,000	10,005,190,000
Liabilities and Equity
Dividends payable	126,487,000				122,847,000				126,487,000	122,847,000
Short-term debt	127,000,000				148,000,000				127,000,000	148,000,000
Other current liabilities	36,000,000				24,453,000				36,000,000	24,453,000
Total current liabilities	289,487,000				295,300,000				289,487,000	295,300,000
Other liabilities	31,616,000				29,192,000				31,616,000	29,192,000
Total other liabilities	31,616,000				29,192,000				31,616,000	29,192,000
Commitments and contingent liabilities
Capitalization
Long-term debt	1,743,181,000				1,492,199,000				1,743,181,000	1,492,199,000
Preferred stockholders' equity	0				104,980,000				0	104,980,000
Common stockholders' equity	8,482,198,000				8,083,519,000				8,482,198,000	8,083,519,000
Total capitalization	10,225,379,000				9,680,698,000				10,225,379,000	9,680,698,000
Total liabilities and equity	10,546,482,000				10,005,190,000				10,546,482,000	10,005,190,000
Other Parent Company Disclosures									(NOTES TO CONDENSED FINANCIAL STATEMENTS Incorporated by reference are Xcel Energy's consolidated statements of common stockholders' equity and OCI in Part II, Item 8. Basis of Presentation - The condensed financial information of Xcel Energy Inc. is presented to comply with Rule 12-04 of Regulation S-X. Xcel Energy Inc.'s investments in subsidiaries are presented under the equity method of accounting. Under this method, the assets and liabilities of subsidiaries are not consolidated. The investments in net assets of the subsidiaries are recorded in the balance sheets. The income from operations of the subsidiaries is reported on a net basis as equity in income of subsidiaries. Related Party Transactions - Xcel Energy Inc. presents its related party receivables net of payables. Accounts receivable and payable with affiliates at Dec. 31 were: 2011 2010 Accounts Accounts Accounts Accounts Thousands of Dollars Receivable Payable Receivable Payable NSP-Minnesota 58,321 - 81,447 - NSP-Wisconsin 8,620 - 12,510 - PSCo 83,263 - 66,828 11,532 SPS 17,440 - 24,769 - Xcel Energy Services Inc. 52,994 1,690 35,311 997 Xcel Energy Ventures Inc. 37,700 - 41,692 - Other subsidiaries of Xcel Energy Inc. 20,574 5,327 20,076 3,784 278,912 7,017 282,633 16,313 Dividends - Cash dividends paid to Xcel Energy Inc. by its subsidiaries were 626 million, 663 million, and 647 million for the years ended Dec. 31, 2011, 2010 and 2009, respectively. See Xcel Energy's notes to the consolidated financial statements in Part II, Item 8 for other disclosures.)
Dividends [Abstract]
Cash dividends paid to Xcel Energy by subsidiaries									626,000,000	663,000,000	647,000,000
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	278,912,000				282,633,000				278,912,000	282,633,000
Accounts Payable	(7,017,000)				(16,313,000)				(7,017,000)	(16,313,000)
Xcel Energy Inc. [Member] | NSP-Minnesota [Member]
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	58,321,000				81,447,000				58,321,000	81,447,000
Accounts Payable	0				0				0	0
Xcel Energy Inc. [Member] | NSP-Wisconsin [Member]
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	8,620,000				12,510,000				8,620,000	12,510,000
Accounts Payable	0				0				0	0
Xcel Energy Inc. [Member] | PSCo [Member]
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	83,263,000				66,828,000				83,263,000	66,828,000
Accounts Payable	0				(11,532,000)				0	(11,532,000)
Xcel Energy Inc. [Member] | SPS [Member]
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	17,440,000				24,769,000				17,440,000	24,769,000
Accounts Payable	0				0				0	0
Xcel Energy Inc. [Member] | Xcel Energy Services Inc. [Member]
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	52,994,000				35,311,000				52,994,000	35,311,000
Accounts Payable	(1,690,000)				(997,000)				(1,690,000)	(997,000)
Xcel Energy Inc. [Member] | Xcel Energy Ventures Inc. [Member]
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	37,700,000				41,692,000				37,700,000	41,692,000
Accounts Payable	0				0				0	0
Xcel Energy Inc. [Member] | Other Subsidiaries [Member]
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts Receivable	20,574,000				20,076,000				20,574,000	20,076,000
Accounts Payable	$ (5,327,000)				$ (3,784,000)				$ (5,327,000)	$ (3,784,000)