Income Taxes - Difference Between Applicable Income Taxes and the Amount Derived by Applying Statutory (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Computed tax expense at statutory federal rate									$ 8,684	$ 15,711	$ 16,371
Tax-exempt income									(384)	(562)	(470)
State tax (net of federal tax benefit)									808	1,045	874
Excess tax benefit – stock based compensation									114	(144)	(848)
Adjustment to net deferred tax assets for enacted changes in tax laws, rates and return to provision adjustments									0	0	(1,895)
Other, net									(366)	(443)	133
Total income tax expense	$ 4,094	$ 3,709	$ 4,010	$ (2,957)	$ 4,202	$ 4,402	$ 4,239	$ 2,764	$ 8,856	$ 15,607	$ 14,165
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory federal rate (as a percent)									21.00%	21.00%	21.00%
Tax-exempt income (as a percent)									(0.90%)	(0.80%)	(0.60%)
State tax (net of federal tax benefit) (as a percent)									1.90%	1.40%	1.10%
Excess tax benefit – stock based compensation (as a percent)									0.30%	(0.20%)	(1.10%)
Adjustment to net deferred tax assets (as a percent)									0.00%	0.00%	(2.40%)
Other, net (as a percent)									(0.90%)	(0.50%)	0.20%
Total income tax expense (as a percent)									21.40%	20.90%	18.20%