Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Due in one year or less, Amortized Cost	$ 76,399
Due after one year through five years, Amortized Cost	275,361
Due after five years through ten years, Amortized Cost	100,146
Due after ten years, Amortized Cost	61,575
Debt securities, available-for-sale, cost (in dollars)	570,080	$ 538,629
Due in one year or less, Fair Value	76,378
Due after one year through five years, Fair Value	274,245
Due after five years through ten years, Fair Value	96,120
Due after ten years, Fair Value	61,592
Debt Securities, Fair Value	564,758	531,325
Mortgage Backed [Member]
Schedule of Investments [Line Items]
Debt securities, available-for-sale, cost (in dollars)	56,599
Debt Securities, Fair Value	$ 56,423	$ 59,383