Income Taxes (Summary Of Income Tax Expense) (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]
Federal									$ 20,090	$ 20,100	$ 20,830
State									1,436	1,166	957
Total current tax expense									21,526	21,266	21,787
Total deferred tax expense									14,909	3,817	6,627
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