Fair Value Measurements (Summary Of The Balances Company Has Elected To Account For At Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Other investments	$ 514,667	$ 549,805
Other assets	4,666	4,379
Other liabilities	$ 16,801	$ 17,383