Derivative Instruments And Hedging Activities (Narrative) (Details) In Millions, unless otherwise specified	1 Months Ended
	Feb. 20, 2013 Oil And Natural Gas Commodity Contracts [Member] USD ($)	Feb. 20, 2013 Interest Rate Swaps [Member] USD ($)	Mar. 31, 2013 Foreign Exchange Contracts [Member] USD ($)	Mar. 31, 2013 Foreign Exchange Contracts [Member] Accrued Liabilities [Member] USD ($)	Mar. 31, 2013 Foreign Exchange Contracts [Member] Other Liabilities [Member] USD ($)	Mar. 31, 2013 Grand Canyon I I I [Member] USD ($)	Mar. 31, 2013 Grand Canyon I I I [Member] NOK	Mar. 31, 2013 Grand Canyon I I [Member] USD ($)	Mar. 31, 2013 Grand Canyon I I [Member] NOK	Mar. 31, 2013 Grand Canyon [Member] USD ($)	Mar. 31, 2013 Grand Canyon [Member] NOK
Liability derivatives designated as hedging instruments			$ 11.1	$ 1.2	$ 9.9
Derivative Cash Settlement	22.5	0.6
Notional Amount of Foreign Currency Derivatives						$ 98.8	595.0	$ 100.4	594.7	$ 104.6	591.3