Fair Value Measurements (Summary Of The Balances Company Has Elected To Account For At Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Other investments	$ 549,805	$ 481,621
Other assets	4,379	3,463
Other liabilities	$ 17,383	$ 9,362