Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Supplemental Cash Flow Information (Textuals)
Interest paid, net of amounts capitalized			$ 116.9	$ 122.4
Income Taxes Paid, Net			3.0	17.6
Accounts payable related to capital expenditures	$ 3.5	$ 3.2	3.5	3.2
Amortization of deferred revenue			20.7	27.8
Equity in Earnings of Unconsolidated Affiliates	14.2	17.5	30.3	34.8
Transmission Affiliate [Member]
Supplemental Cash Flow Information (Textuals)
Equity in Earnings of Unconsolidated Affiliates	14.3	17.5	30.4	34.8
Distributions from transmission affiliate	$ 10.8	$ 14.2	$ 21.2	$ 28.5

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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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.

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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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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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Supplemental Cash Flow Information.

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