Investments - Schedule of Securities in Unrealized Loss Position (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($) Securities	Dec. 31, 2014 USD ($) Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 333,650	$ 237,635
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(19,492)	(6,111)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	98,764	89,832
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(21,450)	(7,209)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	7,979	6,849
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (437)	$ (862)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	17	15
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 2,954	$ 2,303
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (1,681)	$ (197)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	7	1
Fixed-maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 325,671	$ 230,786
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(19,055)	(5,249)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	95,810	87,529
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(19,769)	(7,012)
Fixed-maturity Securities [Member] | U.S. Government and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	693	7,201
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (2)	$ (1)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	1	2
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value		$ 896
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses		$ (54)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities		2
Fixed-maturity Securities [Member] | Foreign Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 43,742	$ 28,038
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (5,434)	$ (1,317)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	44	35
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 32,348	$ 23,330
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (8,338)	$ (2,484)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	53	40
Fixed-maturity Securities [Member] | States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value		$ 1,694
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses		$ (4)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities		3
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 884	$ 2,720
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (493)	$ (184)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	2	4
Fixed-maturity Securities [Member] | Corporates [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 258,836	$ 144,262
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (13,546)	$ (3,818)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	285	153
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 54,429	$ 43,736
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (10,833)	$ (4,007)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	77	78
Fixed-maturity Securities [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 22,400	$ 49,591
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (73)	$ (109)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	24	43
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 8,149	$ 16,847
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (105)	$ (283)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	13	20