Borrowings and Other Financing Instruments (Tables)

12 Months Ended

Dec. 31, 2012

Borrowings and Other Financing Instruments [Abstract]

Credit Facility — In order to use its commercial paper program to fulfill short-term funding needs, NSP-Wisconsin must have a revolving credit facility in place at least equal to the amount of its commercial paper borrowing limit and cannot issue commercial paper in an aggregate amount exceeding available capacity under this credit facility. The line of credit provides short-term financing in the form of notes payable to banks, letters of credit and back-up support for commercial paper borrowings.

At Dec. 31, 2012, NSP-Wisconsin had the following committed credit facility available (in millions):

Credit Facility				Drawn (a)				Available
$	150.0			$	39.0			$	111.0

(a)	Includes outstanding commercial paper.

Commercial Paper [Member]

Borrowings and Other Financing Instruments [Abstract]

Short-Term Borrowings

Commercial Paper — NSP-Wisconsin meets its short-term liquidity requirements primarily through the issuance of commercial paper and borrowings under its credit facility. The following tables present commercial paper outstanding for NSP-Wisconsin:

(Amounts in Millions, Except Interest Rates)	Three Months Ended Dec. 31, 2012
Borrowing limit	$	150
Amount outstanding at period end		39
Average amount outstanding		21
Maximum amount outstanding		101
Weighted average interest rate, computed on a daily basis		0.39	%
Weighted average interest rate at end of period		0.40

(Amounts in Millions, Except Interest Rates)	Twelve Months Ended Dec. 31, 2012			Twelve Months Ended Dec. 31, 2011
Borrowing limit	$	150		$	150
Amount outstanding at period end		39			66
Average amount outstanding		61			24
Maximum amount outstanding		116			70
Weighted average interest rate, computed on a daily basis		0.39	%		0.37	%
Weighted average interest rate at end of period		0.40			0.46

Intercompany Borrowing Arrangement [Member]

Borrowings and Other Financing Instruments [Abstract]

Short-Term Borrowings

Intercompany Borrowing Arrangement — Prior to entering into its credit facility, NSP-Wisconsin had an intercompany borrowing arrangement with NSP-Minnesota, with interest charged at NSP-Minnesota's short-term borrowing rate. The borrowing arrangement terminated in the first quarter 2011, during which time there were no borrowings. The following table presents the intercompany borrowing arrangement with NSP-Minnesota at Dec. 31, 2010:

(Amounts in Millions, Except Interest Rates)	Twelve Months Ended Dec. 31, 2010
Borrowing limit	$	100
Amount outstanding at period end		37
Average amount outstanding		11
Maximum amount outstanding		59
Weighted average interest rate, computed on a daily basis		0.33	%
Weighted average interest rate at end of period		0.38

Notes Payable [Member]

Borrowings and Other Financing Instruments [Abstract]

Short-Term Borrowings

Other Short-Term Borrowings—The following table presents the notes payable of Clearwater Investments, Inc., a NSP-Wisconsin subsidiary, to Xcel Energy Inc.:

(Amounts in Millions, Except Interest Rates)	Dec. 31, 2012			Dec. 31, 2011
Notes payable to affiliates	$	0.6		$	0.5
Weighted average interest rate		0.33	%		0.46	%