Investments, Available-for-sale Securities in a Loss Position (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Rate	Dec. 31, 2017 USD ($) Rate	Dec. 31, 2016 USD ($)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value		$ 89,168
Less than 12 months, gross unrealized holding losses		(558)
12 Months or longer, estimated fair value		125,043
12 Months or longer, gross unrealized holding losses		(1,917)
Total, estimated fair value		214,211
Total, gross unrealized holding losses		(2,475)
Other-than-temporary impairment losses	$ 0	0	$ (276)
Fixed Maturities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value	222,581	78,389
Less than 12 months, gross unrealized holding losses	(2,502)	(327)
12 Months or longer, estimated fair value	128,301	125,043
12 Months or longer, gross unrealized holding losses	(4,366)	(1,917)
Total, estimated fair value	350,882	203,432
Total, gross unrealized holding losses	$ (6,868)	$ (2,244)
Number of securities held	317	195
Number of available-for-sale securities in unrealized loss positions, greater than one year	158	126
Percentage of securities rated A- or better | Rate	86.40%	91.10%
Other-than-temporary impairment losses		$ 0
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value	$ 0	3,497
Less than 12 months, gross unrealized holding losses	0	(2)
12 Months or longer, estimated fair value	499	5,488
12 Months or longer, gross unrealized holding losses	(1)	(12)
Total, estimated fair value	499	8,985
Total, gross unrealized holding losses	(1)	(14)
Obligations of States, Municipalities and Political Subdivisions [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value	42,718	7,258
Less than 12 months, gross unrealized holding losses	(440)	(36)
12 Months or longer, estimated fair value	34,326	38,143
12 Months or longer, gross unrealized holding losses	(854)	(376)
Total, estimated fair value	77,044	45,401
Total, gross unrealized holding losses	(1,294)	(412)
Corporate and Other Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value	62,045	30,944
Less than 12 months, gross unrealized holding losses	(890)	(98)
12 Months or longer, estimated fair value	12,092	13,444
12 Months or longer, gross unrealized holding losses	(511)	(74)
Total, estimated fair value	74,137	44,388
Total, gross unrealized holding losses	(1,401)	(172)
Asset-backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value	93,247	27,609
Less than 12 months, gross unrealized holding losses	(1,017)	(108)
12 Months or longer, estimated fair value	25,746	10,706
12 Months or longer, gross unrealized holding losses	(505)	(160)
Total, estimated fair value	118,993	38,315
Total, gross unrealized holding losses	(1,522)	(268)
Residential Mortgage-backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value	24,571	9,081
Less than 12 months, gross unrealized holding losses	(155)	(83)
12 Months or longer, estimated fair value	55,638	57,262
12 Months or longer, gross unrealized holding losses	(2,495)	(1,295)
Total, estimated fair value	80,209	66,343
Total, gross unrealized holding losses	$ (2,650)	(1,378)
Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value		10,779
Less than 12 months, gross unrealized holding losses		(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)
Number of securities held		13
Number of available-for-sale securities in unrealized loss positions, greater than one year		0
Exchange Traded Fund [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value		$ 130
Less than 12 months, gross unrealized holding losses		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]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, estimated fair value		10,649
Less than 12 months, gross unrealized holding losses		(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)