Investments Maturity Distribution of Debt Securities (Details) - USD ($) $ in Thousands	Mar. 31, 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	$ 50,405
Available-for-sale Securities, Debt Maturities, Due After One Year Through Five Years, Amortized Cost Basis	101,885
Available-for-sale Securities, Debt Maturities, Due After Five Years Through Ten Years, Amortized Cost Basis	119,041
Available-for-sale Securities, Debt Maturities, Due After Ten Years, Amortized Cost Basis	609,771
Available-for-sale Debt Securities, Amortized Cost Basis	881,102	$ 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	50,885
Available-for-sale Securities, Debt Maturities, Due After One Year Through Five Years, Fair Value	104,873
Available-for-sale Securities, Debt Maturities, Due After Five Years Through Ten Years, Fair Value	126,159
Available-for-sale Securities, Debt Maturities, Due After Ten Years, Fair Value	625,299
Available-for-sale Debt Securities, Fair Value	907,216
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	2,526
Held-to-maturity Securities, Debt Maturities, Due After One Year Through Five Years, Amortized Cost Basis	59,799
Held-to-maturity Securities, Debt Maturities, Due After Five Years Through Ten Years, Amortized Cost Basis	40,591
Held-to-maturity Securities, Debt Maturities, Due After Ten Years, Amortized Cost Basis	141,860
Held-to-maturity Securities	244,776	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	2,543
Held-to-maturity Securities, Debt Maturities, Due After One Year Through Five Years, Fair Value	62,061
Held-to-maturity Securities, Debt Maturities, Due After Five Years Through Ten Years, Fair Value	42,255
Held-to-maturity Securities, Debt Maturities, Due After Ten Years, Fair Value	144,841
Held-to-maturity Securities, Fair Value	251,700	252,545
Total Fixed Maturity Securities, Amortized Cost	1,125,878	1,107,477
Total Fixed Maturity Securities, Fair Value	$ 1,158,916	$ 1,134,213