Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Investments in marketable securities	$ 201,346	$ 254,099
Derivatives	14,628	$ 13,557
Total assets	215,974
Liabilities:
Derivatives	536
Level 1 [Member]
Assets:
Investments in marketable securities	1,615
Derivatives	8,322
Total assets	9,937
Liabilities:
Derivatives	0
Level 2 [Member]
Assets:
Investments in marketable securities	199,731
Derivatives	890
Total assets	200,621
Liabilities:
Derivatives	536
Level 3 [Member]
Assets:
Investments in marketable securities	0
Derivatives	5,416
Total assets	5,416
Liabilities:
Derivatives	$ 0