Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Due in one year or less, Amortized Cost	$ 58,057
Due after one year through five years, Amortized Cost	232,118
Due after five years through ten years, Amortized Cost	116,755
Due after ten years, Amortized Cost	55,351
Debt securities, available-for-sale, cost (in dollars)	524,908	$ 450,770
Due in one year or less, Fair Value	57,912
Due after one year through five years, Fair Value	230,320
Due after five years through ten years, Fair Value	113,043
Due after ten years, Fair Value	55,098
Debt Securities, Fair Value	519,163	450,785
Mortgage Backed [Member]
Schedule of Investments [Line Items]
Debt securities, available-for-sale, cost (in dollars)	62,627
Debt Securities, Fair Value	$ 62,790	$ 52,060