Represents the amortization period of a regulatory asset.

No definition available.

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- Definition

Beginning of regulatory asset amortization period

+ References

No definition available.

+ Details

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- Definition

Represents the capacity of an electric generating facility.

+ References

No definition available.

+ Details

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Data Type:	num:powerItemType
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Period Type:	instant

- Definition

Represents the contracted capacity (in megawatts) under a power purchase agreement.

+ References

No definition available.

+ Details

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Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the cash paid for the early termination of an existing contract.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Estimated purchase price for the purchase of Alliant Energy Corporation's natural gas distribution business in southeast Minnesota

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Details

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- Definition

Amount of assets acquired at the acquisition date.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount of other assets expected to be realized or consumed before one year or the normal operating cycle, if longer, acquired at the acquisition date.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of liabilities incurred for goods and services received that are used in an entity's business and related party payables, assumed at the acquisition date.

+ References

+ Details

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- Definition

The amount of inventory recognized as of the acquisition date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

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-Topic 805

-SubTopic 10

-Section 55

-Paragraph 37

-URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount of liabilities assumed at the acquisition date.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

The amount of property, plant, and equipment recognized as of the acquisition date.

+ References

+ Details

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- Definition

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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-Publisher FASB

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-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

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Period Type:	duration

- Details

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ACQUISITIONS (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			0 Months Ended	1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 02, 2014	Mar. 31, 2013 MW
Acquisitions
Purchase price	$ 0	$ 391.6	$ 0
Alliant Energy Corporation's Natural Gas Distribution Business in Southeast Minnesota \| MERC
Acquisitions
Estimated purchase price	14
Fox Energy Company LLC \| WPS
Acquisitions
Purchase price					391.6
Capacity of Electric Generating Facility					593
Assets acquired
Inventories					3.0
Other current assets					0.4
Property, plant, and equipment					374.4
Other long-term assets					15.6
Total assets acquired					393.4
Liabilities assumed
Accounts payable					1.8
Total liabilities assumed					1.8
Contracted Capacity From Power Purchase Agreement					500
Termination of tolling agreement with Fox Energy Company LLC					$ 50.0
Amortization Period of Regulatory Asset	9 years
Beginning of regulatory asset amortization period				Jan. 01, 2014