Income Taxes (Reconciliation Of The Significant Differences Between The Federal Statutory Income Tax Rate And Effective Income Tax Rate) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Computed federal taxes at statutory rate									$ 31,761	$ 27,025	$ 28,879
State income taxes, net of federal tax benefit									1,321	888	887
Tax effects of:
Tax-exempt interest income									(1,098)	(708)	(498)
Bank-owned life insurance									(1,474)	(1,164)	(1,181)
Change in tax rate									7,070	0	0
Other items, net									(1,145)	(958)	327
Income tax expense	$ 14,972	$ 7,003	$ 6,812	$ 7,647	$ 6,338	$ 6,577	$ 6,303	$ 5,866	$ 36,435	$ 25,083	$ 28,414