Income Taxes (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:
Federal									$ 16,769	$ 25,532	$ 23,724
State									8,686	5,025	5,670
Total current									25,455	30,557	29,394
Deferred:
Federal									2,615	12,370	5,497
State									145	893	1,665
Total deferred									2,760	13,263	7,162
Total income tax expense	$ 6,685	$ 8,956	$ 7,451	$ 5,123	$ 21,506	$ 8,725	$ 8,059	$ 5,530	$ 28,215	$ 43,820	$ 36,556