Income Taxes - Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Federal
Current expense, federal	$ 15,553	$ 10,164	$ 9,136
Tax credits/true-up, federal	(5,610)	(3,633)	(5,841)
Change in deferred expense/(benefit), federal	594	1,787	3,730
Income tax expense, federal	10,537	8,318	7,025
State
Current expense, state	3,347	2,936	2,426
Tax credits/true-up, state	(135)	(30)	(175)
Change in deferred expense/(benefit), state	61	84	(32)
Income tax expense, state	3,273	2,990	2,219
Current expense, total	18,900	13,100	11,562
Tax credits/true-up, total	(5,745)	(3,663)	(6,016)
Change in deferred expense/(benefit), total	655	1,871	3,698
Total provision	$ 13,810	$ 11,308	$ 9,244