Income Taxes - Comparison of Federal Statutory Income Tax Rates to Effective Income Tax Rates (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
Amount
Statutory federal tax									$ 11,617	$ 9,703	$ 16,379
State franchise tax, net of federal benefit									5,322	3,488	3,135
Tax-exempt income									(25)	(27)	(297)
Tax impact from change in tax rate									17	(479)	2,591
Stock-based compensation									(27)	(2,643)
Other items, net									(792)	59	(539)
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
Rate
Statutory federal tax									21.00%	21.00%	35.00%
State franchise tax, net of federal benefit									9.60%	7.50%	6.70%
Tax-exempt income									(0.00%)	(0.10%)	(0.60%)
Tax impact from change in tax rate									0.00%	(1.00%)	5.50%
Stock-based compensation									0.00%	(5.70%)	0.00%
Other items, net									(1.40%)	0.10%	(1.20%)
Actual tax expense									29.20%	21.80%	45.40%