Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets:
Investments in equity securities	$ 7,540
Derivatives	24,129	28,666
Total assets	31,669
Liabilities:
Derivatives	7,828	4,947
Level 1 [Member]
Assets:
Investments in equity securities	7,540
Derivatives	12,361
Total assets	19,901
Liabilities:
Derivatives
Level 2 [Member]
Assets:
Investments in equity securities
Derivatives	1,450
Total assets	1,450
Liabilities:
Derivatives	3,721
Level 3 [Member]
Assets:
Derivatives	10,318
Total assets	10,318
Liabilities:
Derivatives	$ 4,107