Investments - Schedule of Securities in Unrealized Loss Position (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) Securities	Dec. 31, 2015 USD ($) Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 67,418	$ 549,243
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(608)	(19,294)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	81,174	49,328
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(3,190)	(8,139)
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	65,666	545,591
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(485)	(19,007)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	77,674	46,119
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(2,739)	(8,044)
U.S. Government and Agencies [Member] | 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	1,729	13,651
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (1)	$ (22)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	1	7
Foreign Government [Member] | 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	$ 3,398	$ 23,572
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (19)	$ (829)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	2	20
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 3,134	$ 2,396
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (87)	$ (693)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	3	3
States and Political Subdivisions [Member] | 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	$ 2,844	$ 2,729
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (34)	$ (44)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	4	6
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value		$ 878
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses		$ (497)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities		2
Corporates [Member] | 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	$ 31,616	$ 413,131
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (321)	$ (17,481)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	29	393
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 58,781	$ 34,624
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (2,519)	$ (6,730)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	65	54
Residential Mortgage-backed Securities [Member] | 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	$ 2,451	$ 9,681
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (39)	$ (61)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	5	9
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 4,515	$ 4,762
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (68)	$ (60)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	8	7
Other Asset-backed Securities [Member] | 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	$ 11,755	$ 26,611
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (53)	$ (77)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	14	23
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 4,108	$ 260
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (32)	$ (2)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	7	2
Commercial Mortgage-backed Securities [Member] | 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	$ 11,873	$ 56,216
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (18)	$ (493)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	11	49
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 7,136	$ 3,199
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (33)	$ (62)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	10	6
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	$ 1,752	$ 3,652
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (123)	$ (287)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	11	17
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 3,500	$ 3,209
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (451)	$ (95)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	9	8