Supplemental Cash Flow Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Supplemental Cash Flow Information (Textuals)
Interest paid, net of amounts capitalized	$ 26.5	$ 12.5
Income taxes paid, net of refunds	15.3
Proceeds from Income Tax Refunds		24.8
Construction Payable, Current	12.6	20.6
Deferred Revenue, Period Increase (Decrease)	(13.7)	(13.2)
Equity in earnings of transmission affiliate	15.6	15.5
Distributions from transmission affiliate	$ 12.9	$ 12.4

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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