Schedule II - Condensed Financial Information of Registrant, Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Cash and cash equivalents	$ 81,747	$ 50,752	$ 24,544	$ 23,958
Deferred income tax asset, net	2,492	6,605
Income taxes receivable	800
Other assets	2,659	2,074
Total assets	667,849	614,389
Liabilities:
Accounts payable and accrued expenses	6,519	8,752
Total liabilities	429,660	404,175
Stockholders' Equity [Abstract]
Common stock	210	210
Additional paid-in capital	155,082	153,353
Retained earnings	73,502	53,640
Accumulated other comprehensive income	9,395	3,011
Stockholders' equity	238,189	210,214	113,451	92,586
Total liabilities and stockholders' equity	667,849	614,389
Parent Company [Member]
Assets
Cash and cash equivalents	1,502	1,868	$ 1,744	$ 2,712
Due from subsidiaries	665	218
Investment in subsidiaries	235,091	207,905
Deferred income tax asset, net	198	627
Income taxes receivable	805	0
Other assets	164	141
Total assets	238,425	210,759
Liabilities:
Accounts payable and accrued expenses	236	428
Income taxes payable	0	117
Total liabilities	236	545
Stockholders' Equity [Abstract]
Common stock	210	210
Additional paid-in capital	155,082	153,353
Retained earnings	73,502	53,640
Accumulated other comprehensive income	9,395	3,011
Stockholders' equity	238,189	210,214
Total liabilities and stockholders' equity	$ 238,425	$ 210,759