Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal									$ 8,074	$ 6,616	$ 12,097
State									5,614	3,451	3,773
Current									13,688	10,067	15,870
Deferred									1,503	(131)	2,492
Deferred tax adjustment for change in tax rate									21	(479)	2,591
Amortization of investment in affordable housing tax credits									900	644	316
Income tax expense	$ 4,149	$ 3,689	$ 4,415	$ 3,859	$ 4,188	$ 2,041	$ 2,292	$ 1,580	$ 16,112	$ 10,101	$ 21,269