Investments Maturity Distribution of Debt Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available-for-sale Securities, Debt Maturities, Due in One Year or Less, Amortized Cost Basis	$ 50,852
Available-for-sale Securities, Debt Maturities, Due After One Year Through Five Years, Amortized Cost Basis	103,179
Available-for-sale Securities, Debt Maturities, Due After Five Years Through Ten Years, Amortized Cost Basis	117,410
Available-for-sale Securities, Debt Maturities, Due After Ten Years, Amortized Cost Basis	631,498
Available-for-sale Debt Securities, Amortized Cost Basis	902,939	$ 860,473
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale Securities, Debt Maturities, Due in One Year or Less, Fair Value	51,396
Available-for-sale Securities, Debt Maturities, Due After One Year Through Five Years, Fair Value	106,605
Available-for-sale Securities, Debt Maturities, Due After Five Years Through Ten Years, Fair Value	124,665
Available-for-sale Securities, Debt Maturities, Due After Ten Years, Fair Value	651,031
Available-for-sale Debt Securities, Fair Value	933,697
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held-to-maturity Securities, Debt Maturities, Due in One Year or Less, Amortized Cost Basis	17,820
Held-to-maturity Securities, Debt Maturities, Due After One Year Through Five Years, Amortized Cost Basis	48,056
Held-to-maturity Securities, Debt Maturities, Due After Five Years Through Ten Years, Amortized Cost Basis	42,472
Held-to-maturity Securities, Debt Maturities, Due After Ten Years, Amortized Cost Basis	133,296
Held-to-maturity Securities	241,644	247,004
Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Held-to-maturity Securities, Debt Maturities, Due in One Year or Less, Fair Value	18,074
Held-to-maturity Securities, Debt Maturities, Due After One Year Through Five Years, Fair Value	49,477
Held-to-maturity Securities, Debt Maturities, Due After Five Years Through Ten Years, Fair Value	44,461
Held-to-maturity Securities, Debt Maturities, Due After Ten Years, Fair Value	136,704
Held-to-maturity Securities, Fair Value	248,716	252,545
Total Fixed Maturity Securities, Amortized Cost	1,144,583	1,107,477
Total Fixed Maturity Securities, Fair Value	$ 1,182,413	$ 1,134,213