Derivative Instruments And Hedging Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 bbl	Apr. 24, 2012
Total volume of oil units	2,900,000
Total Volume Of Gas Units	14,400,000,000
Floor price		100.00
Ceiling price		122.06
Term loans payable	$ 200
Derivative, Net Hedge Ineffectiveness Gain (Loss)	(2.3)
Brent [Member]
Total volume of oil units		1,000,000
Oil And Natural Gas Commodity Contracts [Member]
Future amount to be re-classified to earnings	2.8
Interest Rate Contracts [Member]
Future amount to be re-classified to earnings	$ 0.2