Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Assets:
Investments in equity securities	$ 6,335
Derivatives	30,881	28,666
Total assets	37,216
Liabilities:
Derivatives	5,791	4,947
Level 1 [Member]
Assets:
Investments in equity securities	6,319
Derivatives	6,233
Total assets	12,552
Liabilities:
Derivatives
Level 2 [Member]
Assets:
Investments in equity securities
Derivatives	10,054
Total assets	10,054
Liabilities:
Derivatives	1,655
Level 3 [Member]
Assets:
Investments in equity securities	16
Derivatives	14,594
Total assets	14,610
Liabilities:
Derivatives	$ 4,136