Schedule II - Condensed Financial Information of Registrant, Statements of Income and Comprehensive Income (Loss) (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
Revenues:
Revenues	$ 56,904	$ 60,137	$ 54,947	$ 50,126	$ 50,742	$ 47,839	$ 45,508	$ 42,687	$ 222,114	$ 186,776	$ 141,615
Expenses [Abstract]
Other expenses									168	429	2,567
Interest expense											1,300
Total expenses									181,634	148,255	102,079
Income tax benefit									6,693	13,620	13,369
Net income	4,448	11,940	10,112	7,287	5,924	4,201	8,495	6,281	33,787	24,901	26,167
Other Comprehensive Income (Loss) [Abstract]
Total comprehensive income	$ 6,804	$ 9,987	$ 9,096	$ 2,431	$ 7,422	$ 5,840	$ 10,669	$ 7,354	28,318	31,285	25,527
Parent Company [Member]
Revenues:
Revenues									3,215	2,037	1,815
Expenses [Abstract]
Other operating expenses									2,457	2,526	2,395
Other expenses									1,598	652	492
Interest expense									0	0	1,339
Total expenses									4,055	3,178	4,226
Loss before equity in net income of subsidiaries									(840)	(1,141)	(2,411)
Income tax benefit									(1,158)	(739)	(844)
Loss before equity in net income of subsidiaries									318	(402)	(1,567)
Equity in net income of subsidiaries									33,469	25,303	27,734
Net income									33,787	24,901	26,167
Other Comprehensive Income (Loss) [Abstract]
Equity in other comprehensive earnings (losses) of subsidiaries									(5,469)	6,384	(640)
Total comprehensive income									$ 28,318	$ 31,285	$ 25,527