Investments Gross Unrealized Gains and Losses (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017	Jun. 30, 2018 USD ($)	Jun. 30, 2017	Dec. 31, 2017 USD ($)
Gross Unrealized Gains and Losses [Line Items]
Number of Equity Securities Sold	0	0	0	1
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 967,918		$ 967,918		$ 935,977
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	23,700		23,700		41,729
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	15,167		15,167		3,097
Available-for-sale Securities, Debt Securities	976,451		976,451		974,609
Held-to-maturity Securities [Abstract]
Held-to-maturity securities	214,514		214,514		233,961
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	5,643		5,643		8,703
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	1,383		1,383		1,287
Fixed maturities held-to-maturity, fair value	218,774		218,774		241,377
Total Fixed Maturity Securities, Amortized Cost	1,182,432		1,182,432		1,169,938
Debt Securities, Accumulative Gross Unrealized and Unrecognized Gains	29,343		29,343		50,432
Debt Securities, Accumulated Gross Unrealized and Unrecognized Losses	16,550		16,550		4,384
Total Fixed Maturity Securities, Fair Value	1,195,225		1,195,225		1,215,986
Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	15,167		15,167		3,097
Held-to-maturity Securities [Abstract]
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	1,383		1,383		1,287
US Treasury Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Available-for-sale Debt Securities, Amortized Cost Basis	9,824		9,824		9,860
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	1,500		1,500		1,948
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	0		0		0
Available-for-sale Securities, Debt Securities	11,324		11,324		11,808
US Government Agencies Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Available-for-sale Debt Securities, Amortized Cost Basis	3,558		3,558		3,570
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	741		741		926
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	0		0		0
Available-for-sale Securities, Debt Securities	4,299		4,299		4,496
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Available-for-sale Debt Securities, Amortized Cost Basis	550,700		550,700		550,536
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	12,009		12,009		18,507
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	3,170		3,170		1,540
Available-for-sale Securities, Debt Securities	559,539		559,539		567,503
Held-to-maturity Securities [Abstract]
Held-to-maturity securities	198,439		198,439		213,054
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	5,112		5,112		7,585
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	772		772		629
Fixed maturities held-to-maturity, fair value	202,779		202,779		220,010
Foreign Government Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Available-for-sale Debt Securities, Amortized Cost Basis	103		103		103
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	16		16		18
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	0		0		0
Available-for-sale Securities, Debt Securities	119		119		121
Corporate Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Available-for-sale Debt Securities, Amortized Cost Basis	402,213		402,213		370,043
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	9,353		9,353		20,212
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	11,994		11,994		1,552
Available-for-sale Securities, Debt Securities	399,572		399,572		388,703
Held-to-maturity Securities [Abstract]
Held-to-maturity securities	16,075		16,075		20,907
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	531		531		1,118
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	611		611		658
Fixed maturities held-to-maturity, fair value	15,995		15,995		21,367
Residential Mortgage Backed Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis [Abstract]
Available-for-sale Debt Securities, Amortized Cost Basis	1,520		1,520		1,865
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	81		81		118
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	3		3		5
Available-for-sale Securities, Debt Securities	$ 1,598		$ 1,598		$ 1,978