Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Due in one year or less, Amortized Cost	$ 81,699
Due after one year through five years, Amortized Cost	297,438
Due after five years through ten years, Amortized Cost	97,531
Due after ten years, Amortized Cost	56,373
Debt securities, available-for-sale, cost (in dollars)	597,890	$ 538,629
Due in one year or less, Fair Value	81,687
Due after one year through five years, Fair Value	298,846
Due after five years through ten years, Fair Value	98,574
Due after ten years, Fair Value	56,581
Debt Securities, Fair Value	600,791	531,325
Mortgage Backed [Member]
Schedule of Investments [Line Items]
Debt securities, available-for-sale, cost (in dollars)	64,849
Debt Securities, Fair Value	$ 65,103	$ 59,383