Investments - Schedule of Securities in Unrealized Loss Position (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($) Securities	Dec. 31, 2016 USD ($) Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position, less than 12 months, fair value	$ 282,321	$ 380,199
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(2,829)	(5,207)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	35,786	62,955
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(1,358)	(2,568)
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	281,918	376,020
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	(2,818)	(4,938)
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	35,384	61,103
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	(1,269)	(2,324)
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	5,247	3,668
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (16)	$ (24)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	6	4
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	$ 29,301	$ 34,538
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (314)	$ (526)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	32	36
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 1,272	$ 3,048
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (44)	$ (161)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	2	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	$ 8,187	$ 8,902
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (92)	$ (129)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	10	12
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	$ 145,814	$ 232,070
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (1,885)	$ (3,484)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	125	225
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 22,838	$ 45,471
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (1,149)	$ (2,045)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	29	51
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	$ 15,066	$ 15,232
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (97)	$ (92)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	8	9
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 2,493	$ 3,606
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (19)	$ (28)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	9	9
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	$ 42,259	$ 48,275
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (148)	$ (260)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	43	45
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 1,196	$ 1,315
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (7)	$ (43)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	2	3
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	$ 36,044	$ 33,335
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (266)	$ (423)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	32	33
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 7,585	$ 7,663
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (50)	$ (47)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	11	11
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	$ 403	$ 4,179
Available-for-sale securities, continuous unrealized loss position, less than 12 months, aggregate losses	$ (11)	$ (269)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, less than one year | Securities	9	12
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, fair value	$ 402	$ 1,852
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, aggregate losses	$ (89)	$ (244)
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year | Securities	7	8