Supplemental Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Supplemental Cash Flow Information (Textuals)
Interest paid, net of amounts capitalized	$ 20.3us-gaap_InterestPaidNet	$ 21.2us-gaap_InterestPaidNet
Income Taxes Paid, Net	4.3us-gaap_IncomeTaxesPaidNet	10.0us-gaap_IncomeTaxesPaidNet
Accounts payable related to capital expenditures	1.6us-gaap_ConstructionPayableCurrent	2.4us-gaap_ConstructionPayableCurrent
Amortization of deferred revenue	11.1	13.9
Income (Loss) from Equity Method Investments	16.1	17.3
Distributions from transmission affiliate	10.4	14.3
Transmission Affiliate [Member]
Supplemental Cash Flow Information (Textuals)
Income (Loss) from Equity Method Investments	$ 16.1	$ 17.3

Carrying value as of the balance sheet date of obligations incurred and payable for the acquisition of merchandise, materials, supplies and services pertaining to construction projects such as a housing development or factory expansion not classified as trade payables. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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-Number 210

-Section 02

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-Subparagraph a

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-Name Accounting Standards Codification

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(a))

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Amount of previously reported deferred or unearned revenue that was recognized as revenue during the period. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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This item represents disclosure of the amount of dividends or other distributions received from unconsolidated subsidiaries, certain corporate joint ventures, and certain noncontrolled corporation; these investments are accounted for under the equity method of accounting. This element excludes distributions that constitute a return of investment, which are classified as investing activities.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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The amount of cash paid for interest during the period net of cash paid for interest that is capitalized.

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