Summary of Investments (Fair Value of Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fixed maturities:
Amortized Cost	$ 1,663,984	$ 1,761,289
Gross Unrealized Appreciation	66,172	11,844
Gross Unrealized Depreciation	870	23,645
Fair Value	1,729,286	1,749,488
U.S. Treasury
Fixed maturities:
Amortized Cost	38,863	27,632
Gross Unrealized Appreciation	225	6
Gross Unrealized Depreciation	26	220
Fair Value	39,062	27,418
U.S. government agency
Fixed maturities:
Amortized Cost	110,971	215,535
Gross Unrealized Appreciation	2,821	896
Gross Unrealized Depreciation	61	1,749
Fair Value	113,731	214,682
Foreign bonds
Fixed maturities:
Amortized Cost	4,938	9,698
Gross Unrealized Appreciation	181	31
Gross Unrealized Depreciation	0	13
Fair Value	5,119	9,716
Public utilities
Fixed maturities:
Amortized Cost	62,724	56,808
Gross Unrealized Appreciation	2,779	274
Gross Unrealized Depreciation	0	1,023
Fair Value	65,503	56,059
Mortgage-backed securities
Fixed maturities:
Amortized Cost	6,649	7,642
Gross Unrealized Appreciation	135	14
Gross Unrealized Depreciation	32	232
Fair Value	6,752	7,424
Collateralized mortgage obligations | Government National Mortgage Association (GNMA) Insured Loans
Fixed maturities:
Amortized Cost	74,450	78,055
Gross Unrealized Appreciation	3,239	380
Gross Unrealized Depreciation	51	1,734
Fair Value	77,638	76,701
Collateralized mortgage obligations | Federal Home Loan Mortgage Corporation (FHLMC) Insured Loans
Fixed maturities:
Amortized Cost	125,422	108,403
Gross Unrealized Appreciation	2,507	524
Gross Unrealized Depreciation	196	1,304
Fair Value	127,733	107,623
Collateralized mortgage obligations | Federal National Mortgage Association (FNMA) Insured Loans
Fixed maturities:
Amortized Cost	71,874	53,267
Gross Unrealized Appreciation	2,377	213
Gross Unrealized Depreciation	79	732
Fair Value	74,172	52,748
Asset-backed securities
Fixed maturities:
Amortized Cost	3,240	3,256
Gross Unrealized Appreciation	483	352
Gross Unrealized Depreciation	63	113
Fair Value	3,660	3,495
General obligations | States, municipalities and political subdivisions | Midwest
Fixed maturities:
Amortized Cost	86,609	94,806
Gross Unrealized Appreciation	3,079	1,091
Gross Unrealized Depreciation	0	685
Fair Value	89,688	95,212
General obligations | States, municipalities and political subdivisions | Northeast
Fixed maturities:
Amortized Cost	31,159	37,326
Gross Unrealized Appreciation	1,216	432
Gross Unrealized Depreciation	0	103
Fair Value	32,375	37,655
General obligations | States, municipalities and political subdivisions | South
Fixed maturities:
Amortized Cost	112,667	114,710
Gross Unrealized Appreciation	3,482	754
Gross Unrealized Depreciation	0	1,553
Fair Value	116,149	113,911
General obligations | States, municipalities and political subdivisions | West
Fixed maturities:
Amortized Cost	105,774	107,787
Gross Unrealized Appreciation	4,807	1,229
Gross Unrealized Depreciation	0	1,175
Fair Value	110,581	107,841
Special revenue | States, municipalities and political subdivisions | Midwest
Fixed maturities:
Amortized Cost	137,191	140,025
Gross Unrealized Appreciation	6,474	1,609
Gross Unrealized Depreciation	0	870
Fair Value	143,665	140,764
Special revenue | States, municipalities and political subdivisions | Northeast
Fixed maturities:
Amortized Cost	60,091	62,737
Gross Unrealized Appreciation	3,129	452
Gross Unrealized Depreciation	0	1,241
Fair Value	63,220	61,948
Special revenue | States, municipalities and political subdivisions | South
Fixed maturities:
Amortized Cost	227,301	237,848
Gross Unrealized Appreciation	11,211	1,669
Gross Unrealized Depreciation	0	3,708
Fair Value	238,512	235,809
Special revenue | States, municipalities and political subdivisions | West
Fixed maturities:
Amortized Cost	138,858	143,829
Gross Unrealized Appreciation	6,504	1,294
Gross Unrealized Depreciation	0	2,203
Fair Value	145,362	142,920
Energy | Corporate bonds
Fixed maturities:
Amortized Cost	26,613	28,909
Gross Unrealized Appreciation	1,333	43
Gross Unrealized Depreciation	0	304
Fair Value	27,946	28,648
Industrials | Corporate bonds
Fixed maturities:
Amortized Cost	53,118	53,867
Gross Unrealized Appreciation	1,803	124
Gross Unrealized Depreciation	23	906
Fair Value	54,898	53,085
Consumer goods and services | Corporate bonds
Fixed maturities:
Amortized Cost	47,667	54,323
Gross Unrealized Appreciation	2,295	142
Gross Unrealized Depreciation	9	819
Fair Value	49,953	53,646
Health care | Corporate bonds
Fixed maturities:
Amortized Cost	13,990	16,721
Gross Unrealized Appreciation	704	42
Gross Unrealized Depreciation	0	105
Fair Value	14,694	16,658
Technology, media and telecommunications | Corporate bonds
Fixed maturities:
Amortized Cost	25,899	26,819
Gross Unrealized Appreciation	1,542	35
Gross Unrealized Depreciation	0	678
Fair Value	27,441	26,176
Financial services | Corporate bonds
Fixed maturities:
Amortized Cost	97,916	81,286
Gross Unrealized Appreciation	3,846	238
Gross Unrealized Depreciation	330	2,175
Fair Value	$ 101,432	$ 79,349