v2.4.0.6

Summary Of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2012

Accounting Policies [Abstract]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy								IPL								WPL
	September 30, 2012				December 31, 2011				September 30, 2012				December 31, 2011				September 30, 2012				December 31, 2011
Tax-related		$709.4				$634.7				$686.2				$614.6				$23.2				$20.1
Pension and other postretirement benefits costs	495.4				514.1				256.3				264.9				239.1				249.2
Asset retirement obligations (AROs)	57.8				65.9				38.7				48.7				19.1				17.2
Derivatives	56.6				77.7				22.6				33.5				34.0				44.2
Environmental-related costs	36.3				38.9				31.5				32.2				4.8				6.7
Emission allowances	30.0				30.0				30.0				30.0				—				—
Debt redemption costs	20.3				21.8				14.0				15.1				6.3				6.7
IPL’s electric transmission service costs	18.7				24.9				18.7				24.9				—				—
Proposed base-load projects costs	16.0				21.5				11.4				15.3				4.6				6.2
Other	77.9				65.5				41.6				38.1				36.3				27.4
		$1,518.4				$1,495.0				$1,151.0				$1,117.3				$367.4				$377.7

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy								IPL								WPL
	September 30, 2012				December 31, 2011				September 30, 2012				December 31, 2011				September 30, 2012				December 31, 2011
Cost of removal obligations		$406.6				$404.9				$266.5				$261.9				$140.1				$143.0
IPL’s tax benefit rider	327.4				349.6				327.4				349.6				—				—
Energy conservation cost recovery	48.8				29.6				8.9				4.7				39.9				24.9
IPL’s electric transmission assets sale	35.2				45.1				35.2				45.1				—				—
Derivatives	21.3				7.2				10.2				3.6				11.1				3.6
Commodity cost recovery	20.4				23.8				14.8				23.2				5.6				0.6
Other	46.7				49.9				25.1				33.2				21.6				16.7
		$906.4				$910.1				$688.1				$721.3				$218.3				$188.8

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- Definition

Tabular disclosure of assets that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 715

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501251&loc=d3e52485-110419



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44264-110382



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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Tabular disclosure of regulatory liabilities. Detailed information about liabilities that result from rate actions of a regulator. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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