Income Taxes - Components of Income Taxes (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									$ 22,658	$ 28,380	$ 31,679
State									2,625	1,354	2,131
Total									25,283	29,734	33,810
Deferred
Federal									13,369	22,314	10,480
State									3,075	1,147	557
Revaluation of net deferred tax assets as a result of the Tax Cuts and Jobs Act									0	14,486	0
Total									16,444	37,947	11,037
Total income tax expense	$ 13,098	$ 8,532	$ 10,424	$ 9,673	$ 30,234	$ 14,199	$ 11,993	$ 11,255	$ 41,727	$ 67,681	$ 44,847