Income Taxes (Schedule Of Components Of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S. federal, Current	$ 89,154	$ 116,753	$ 102,607
State and local, Current	7,735	9,457	6,551
Current, income tax expense (benefit)	96,889	126,210	109,158
U.S. federal, Deferred	12,190	(2,036)	7,084
State and local, Deferred	1,427	(23)	348
Deferred, income tax expense (benefit)	13,617	(2,059)	7,432
U.S. federal, Total	101,344	114,717	109,691
State and local, Total	9,162	9,434	6,899
Total income tax expense	$ 110,506	$ 124,151	$ 116,590