Income Taxes - Reconciliation between Federal Statutory Income Tax Rate and Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%
State income taxes, net of the federal tax effect	6.80%	7.00%	7.20%
Meals and entertainment	0.10%	0.40%	0.30%
Disallowed officer's compensation	0.20%	0.20%	0.20%
FDIC premiums	0.30%	0.20%	0.50%
Share-based compensation expense on incentive stock options and ESPP	(0.30%)	(0.60%)	(1.40%)
Qualified affordable housing project tax credits	(0.50%)	(0.30%)	(0.30%)
Tax-exempt interest income	(0.80%)	(0.60%)	(0.60%)
Other, net	0.20%	(0.10%)	(0.40%)
Effective income tax rate	27.00%	27.20%	26.50%