Income Taxes (Schedule of Components of Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current tax expense:
Federal									$ 15,460	$ 23,827	$ 19,444
State									2,863	2,201	2,061
Total current tax expense									18,323	26,028	21,505
Deferred tax expense (benefit):
Federal									63	5,717	796
State									(126)	(30)	72
Total deferred tax (benefit) expense									(63)	5,687	868
Total income tax expense	$ 4,523	$ 4,741	$ 4,742	$ 4,254	$ 13,163	$ 6,326	$ 6,505	$ 5,721	$ 18,260	$ 31,715	$ 22,373