Price Risk Management Assets And Liabilities (Interest Rate Swaps Outstanding) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2011		Dec. 31, 2010
Fixed Interest Rate Of 3.64% [Member]
Term, years	10
Fixed Interest Rate Of 3.64% [Member] | Derivatives Not Designated As Hedging Instruments - Interest Rate Derivatives [Member]
Term, years	August 2012 (2)	[1]
Notional Amount	$ 400,000	[1]	$ 400,000	[1]
Type	Forward starting to pay a fixed rate of 3.64% and receive a floating rate	[1],[2]
Fixed rate	3.64%
Floating Interest Rate Of 6.70% [Member] | Derivatives Not Designated As Hedging Instruments - Interest Rate Derivatives [Member]
Term, years	July 2018
Notional Amount	500,000		500,000
Type	Pay a floating rate plus a spread and receive a fixed rate of 6.70%	[2]
Fixed rate	6.70%
Fixed Interest Rate Of 4.13% [Member]
Term, years	10
Fixed Interest Rate Of 4.13% [Member] | Derivatives Not Designated As Hedging Instruments - Interest Rate Derivatives [Member]
Term, years	July 2013 (3)	[3]
Notional Amount	$ 200,000	[3]
Type	Forward starting to pay a fixed rate of 4.13% and receive a floating rate	[2],[3]
Fixed rate	4.13%

[1] These forward starting swaps have an effective date of August 2012 and a term of 10 years; however, the swaps have a mandatory termination provision and will be settled in August 2012.

[2] Floating rates are based on LIBOR.

[3] These forward starting swaps have an effective date of July 2013 and a term of 10 years; however, the swaps have a mandatory termination provision and will be settled in July 2013.