Investments Available-for-Sale Securities in a Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value	$ 169,349	$ 89,168
Gross unrealized holding losses, less than 12 months	(2,033)	(558)
12 Months or Longer, Estimated Fair Value	112,482	125,043
12 Months or Longer, Gross Unrealized Holding Losses	(4,089)	(1,917)
Total Estimated Fair Value	281,831	214,211
Total Gross Unrealized Holding Losses	(6,122)	(2,475)
Total fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value		78,389
Gross unrealized holding losses, less than 12 months		(327)
12 Months or Longer, Estimated Fair Value		125,043
12 Months or Longer, Gross Unrealized Holding Losses		(1,917)
Total Estimated Fair Value	281,800	203,432
Total Gross Unrealized Holding Losses	(6,100)	(2,244)
U.S. Treasury securities and obligations of U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value	0	3,497
Gross unrealized holding losses, less than 12 months	0	(2)
12 Months or Longer, Estimated Fair Value	494	5,488
12 Months or Longer, Gross Unrealized Holding Losses	(4)	(12)
Total Estimated Fair Value	494	8,985
Total Gross Unrealized Holding Losses	(4)	(14)
Obligations of states, municipalities and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value	56,436	7,258
Gross unrealized holding losses, less than 12 months	(849)	(36)
12 Months or Longer, Estimated Fair Value	37,173	38,143
12 Months or Longer, Gross Unrealized Holding Losses	(1,183)	(376)
Total Estimated Fair Value	93,609	45,401
Total Gross Unrealized Holding Losses	(2,032)	(412)
Corporate and other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value	50,879	30,944
Gross unrealized holding losses, less than 12 months	(461)	(98)
12 Months or Longer, Estimated Fair Value	10,643	13,444
12 Months or Longer, Gross Unrealized Holding Losses	(117)	(74)
Total Estimated Fair Value	61,522	44,388
Total Gross Unrealized Holding Losses	(578)	(172)
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value	41,534	27,609
Gross unrealized holding losses, less than 12 months	(419)	(108)
12 Months or Longer, Estimated Fair Value	10,006	10,706
12 Months or Longer, Gross Unrealized Holding Losses	(262)	(160)
Total Estimated Fair Value	51,540	38,315
Total Gross Unrealized Holding Losses	(681)	(268)
Residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value	20,500	9,081
Gross unrealized holding losses, less than 12 months	(304)	(83)
12 Months or Longer, Estimated Fair Value	54,166	57,262
12 Months or Longer, Gross Unrealized Holding Losses	(2,523)	(1,295)
Total Estimated Fair Value	74,666	66,343
Total Gross Unrealized Holding Losses	$ (2,827)	(1,378)
Total equity securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value		10,779
Gross unrealized holding losses, less than 12 months		(231)
12 Months or Longer, Estimated Fair Value		0
12 Months or Longer, Gross Unrealized Holding Losses		0
Total Estimated Fair Value		10,779
Total Gross Unrealized Holding Losses		(231)
Exchange traded funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value		130
Gross unrealized holding losses, less than 12 months		0
12 Months or Longer, Estimated Fair Value		0
12 Months or Longer, Gross Unrealized Holding Losses		0
Total Estimated Fair Value		130
Total Gross Unrealized Holding Losses		0
Nonredeemable preferred stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Estimated Fair Value		10,649
Gross unrealized holding losses, less than 12 months		(231)
12 Months or Longer, Estimated Fair Value		0
12 Months or Longer, Gross Unrealized Holding Losses		0
Total Estimated Fair Value		10,649
Total Gross Unrealized Holding Losses		$ (231)