Parent Company Only Financial Statements - Parent Company Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 29,540	$ 25,866	$ 15,001
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	8,768	8,729	9,856
Stock-based compensation cost	1,750	1,847	938
Net cash provided (used) by operating activities	19,248	53,553	47,890
Investing Activities
Net cash provided (used) by investing activities	(65,594)	(154,708)	(205,093)
Financing Activities
Repurchase of common stock	(1,948)	(356)	(294)
Proceeds from the issuance of common stock in initial public offering net of issuance costs	62,804
Net cash provided (used) by financing activities	149,701	19,808	71,834
Net change in cash and cash equivalents	103,355	(81,347)	(85,369)
Cash and cash equivalents at beginning of period	40,651	121,998	207,367
Cash and cash equivalents at end of period	144,006	40,651	121,998
Parent Company
Operating Activities
Net income	29,540	25,866	15,001
Adjustments to reconcile net income to net cash provided by operating activities
Equity in undistributed income of subsidiaries	(19,089)	(18,852)	(10,755)
Depreciation and amortization	115	116	116
Stock-based compensation cost	251	370	315
Other, net	2,676	1,314	4,904
Net cash provided (used) by operating activities	13,493	8,814	9,581
Financing Activities
Cash dividends paid on common stock	(8,909)	(7,456)	(6,729)
Repurchase of common stock	(1,948)	(356)	(294)
Proceeds from the issuance of common stock in initial public offering net of issuance costs	62,804
Net cash provided (used) by financing activities	51,947	(7,812)	(7,023)
Net change in cash and cash equivalents	65,440	1,002	2,558
Cash and cash equivalents at beginning of period	8,207	7,205	4,647
Cash and cash equivalents at end of period	$ 73,647	$ 8,207	$ 7,205