Investments - Schedule of Gross Unrealized Losses and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 393,144	$ 492,187
Less Than 12 Months, Gross Unrealized Losses	(4,558)	(9,100)
12 Months or More, Fair Value	43,897	54,560
12 Months or More, Gross Unrealized Losses	(2,776)	(4,487)
Total, Fair Value	437,041	546,747
Total, Gross Unrealized Losses	(7,334)	(13,587)
Fixed maturity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	390,316	470,842
Less Than 12 Months, Gross Unrealized Losses	(4,512)	(8,029)
12 Months or More, Fair Value	37,148	48,002
12 Months or More, Gross Unrealized Losses	(1,383)	(2,903)
Total, Fair Value	427,464	518,844
Total, Gross Unrealized Losses	(5,895)	(10,932)
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	21,105	28,398
Less Than 12 Months, Gross Unrealized Losses	(409)	(984)
12 Months or More, Fair Value	707	0
12 Months or More, Gross Unrealized Losses	(23)	0
Total, Fair Value	21,812	28,398
Total, Gross Unrealized Losses	(432)	(984)
Residential mortgage-backed
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	79,778	93,242
Less Than 12 Months, Gross Unrealized Losses	(1,143)	(1,548)
12 Months or More, Fair Value	29,827	32,330
12 Months or More, Gross Unrealized Losses	(1,184)	(1,427)
Total, Fair Value	109,605	125,572
Total, Gross Unrealized Losses	(2,327)	(2,975)
Corporate
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	138,683	199,841
Less Than 12 Months, Gross Unrealized Losses	(2,111)	(4,212)
12 Months or More, Fair Value	1,617	8,477
12 Months or More, Gross Unrealized Losses	(171)	(1,449)
Total, Fair Value	140,300	208,318
Total, Gross Unrealized Losses	(2,282)	(5,661)
Commercial mortgage and asset-backed
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	50,374	47,990
Less Than 12 Months, Gross Unrealized Losses	(518)	(799)
12 Months or More, Fair Value	4,997	7,195
12 Months or More, Gross Unrealized Losses	(5)	(27)
Total, Fair Value	55,371	55,185
Total, Gross Unrealized Losses	(523)	(826)
Obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	52,122	50,573
Less Than 12 Months, Gross Unrealized Losses	(141)	(85)
12 Months or More, Fair Value	0	0
12 Months or More, Gross Unrealized Losses	0	0
Total, Fair Value	52,122	50,573
Total, Gross Unrealized Losses	(141)	(85)
U.S. Treasury securities and obligations guaranteed by the U.S. government
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	48,254	48,989
Less Than 12 Months, Gross Unrealized Losses	(190)	(185)
12 Months or More, Fair Value	0	0
12 Months or More, Gross Unrealized Losses	0	0
Total, Fair Value	48,254	48,989
Total, Gross Unrealized Losses	(190)	(185)
Redeemable preferred stock
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value		1,809
Less Than 12 Months, Gross Unrealized Losses		(216)
12 Months or More, Fair Value		0
12 Months or More, Gross Unrealized Losses		0
Total, Fair Value		1,809
Total, Gross Unrealized Losses		(216)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	2,828	21,345
Less Than 12 Months, Gross Unrealized Losses	(46)	(1,071)
12 Months or More, Fair Value	6,749	6,558
12 Months or More, Gross Unrealized Losses	(1,393)	(1,584)
Total, Fair Value	9,577	27,903
Total, Gross Unrealized Losses	$ (1,439)	$ (2,655)