Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Supplemental Cash Flow Information (Details)

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Summary of Significant Accounting Policies - Supplemental Cash Flow Information (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Accounting Policies [Abstract]      
Expenditures Included In Construction Trade Payables $ 7.1 $ 13.7 $ 31.8
Interest Paid, Net $ 46.8 $ 45.4 $ 37.6