Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets:
Investments in marketable securities	$ 113,150	$ 201,910
Derivatives	6,153	$ 9,052
Total assets	119,303
Liabilities:
Derivatives	355
Level 1 [Member]
Assets:
Investments in marketable securities	1,699
Derivatives	1,960
Total assets	3,659
Liabilities:
Derivatives	224
Level 2 [Member]
Assets:
Investments in marketable securities	111,451
Derivatives	220
Total assets	111,671
Liabilities:
Derivatives	0
Level 3 [Member]
Assets:
Investments in marketable securities	0
Derivatives	3,973
Total assets	3,973
Liabilities:
Derivatives	$ 131