Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Fixed maturity securities, fair value	$ 620,781	$ 662,276
Fixed maturity securities, cost	460,497	376,109
Equity securities, cost	$ 0	$ 0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	20,488,385	20,388,396
Common stock, shares outstanding	19,230,135	19,130,146
Treasury stock, shares	1,258,250	1,258,250