Schedule II - Condensed Financial Information of Registrant, Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income	$ 4,448	$ 11,940	$ 10,112	$ 7,287	$ 5,924	$ 4,201	$ 8,495	$ 6,281	$ 33,787	$ 24,901	$ 26,167
Adjustments to reconcile net income to net cash used in operating activities:
Deferred tax expense (benefit)									(3,230)	1,065	561
Stock compensation expense									1,597	652	492
Net Cash Provided by (Used in) Investing Activities [Abstract]
Dividends received from subsidiary									11,500
Financing activities:
Common stock issued, net of transaction costs									0	0	72,841
Common stock issued, stock options exercised									1,808	1,077	0
Dividends paid									(5,906)	(5,039)	(2,097)
Repayment of note payable									0	0	(30,000)
Net cash (used in) provided by financing activities									(4,098)	(3,971)	40,611
Net change in cash and cash equivalents									(6,658)	30,995	26,208
Cash and cash equivalents at beginning of period				81,747				50,752	81,747	50,752	24,544
Cash and cash equivalents at end of period	75,089				81,747				75,089	81,747	50,752
Parent Company [Member]
Operating activities:
Net income									33,787	24,901	26,167
Adjustments to reconcile net income to net cash used in operating activities:
Deferred tax expense (benefit)									(170)	429	(65)
Stock compensation expense									1,597	652	492
Equity in undistributed earnings of subsidiaries									(33,469)	(25,303)	(27,734)
Changes in operating assets and liabilities									(633)	(1,583)	520
Net cash provided by (used in) operating activities									1,112	(904)	(620)
Net Cash Provided by (Used in) Investing Activities [Abstract]
Dividends received from subsidiary									11,500	4,500	0
Contribution to subsidiary									0	0	(40,000)
Net cash provided by (used in) investing activities									11,500	4,500	(40,000)
Financing activities:
Common stock issued, net of transaction costs									0	0	72,841
Common stock issued, stock options exercised									1,808	1,077	0
Dividends paid									(5,906)	(5,039)	(2,097)
Repayment of note payable									0	0	(30,000)
Net cash (used in) provided by financing activities									(4,098)	(3,962)	40,744
Net change in cash and cash equivalents									8,514	(366)	124
Cash and cash equivalents at beginning of period				$ 1,502				$ 1,868	1,502	1,868	1,744
Cash and cash equivalents at end of period	$ 10,016				$ 1,502				$ 10,016	$ 1,502	$ 1,868