Income Taxes - Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Federal
Current expense, federal	$ 9,136	$ 5,677	$ 14,627
Tax credits/true-up, federal	(5,841)	(5,573)	(312)
Change in deferred expense/(benefit), federal	3,730	1,700	(369)
Income tax expense, federal	7,025	1,804	13,946
State
Current expense, state	2,426	1,662	2,368
Tax credits/true-up, state	(175)	(383)	0
Change in deferred expense/(benefit), state	(32)	542	(467)
Income tax expense, state	2,219	1,821	1,901
Current expense, total	11,562	7,339	16,995
Tax credits/true-up, total	(6,016)	(5,956)	(312)
Change in deferred expense/(benefit), total	3,698	2,242	(836)
Total provision	$ 9,244	$ 3,625	$ 15,847