Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Assets:
Investments in equity securities	$ 8,035
Derivatives	60,195	24,129
Total assets	68,230
Liabilities:
Derivatives	7,090	7,828
Level 1 [Member]
Assets:
Investments in equity securities	8,035
Derivatives	51,701
Total assets	59,736
Level 2 [Member]
Assets:
Derivatives	1,650
Total assets	1,650
Liabilities:
Derivatives	5,355
Level 3 [Member]
Assets:
Derivatives	6,844
Total assets	6,844
Liabilities:
Derivatives	$ 1,735