Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Due in one year or less, Amortized Cost	$ 51,034
Due after one year through five years, Amortized Cost	196,816
Due after five years through ten years, Amortized Cost	106,014
Due after ten years, Amortized Cost	45,994
Debt securities, available-for-sale, cost (in dollars)	466,976	450,770
Due in one year or less, Fair Value	51,292
Due after one year through five years, Fair Value	198,058
Due after five years through ten years, Fair Value	104,179
Due after ten years, Fair Value	46,104
Debt Securities, Fair Value	467,057	450,785
Mortgage Backed [Member]
Schedule of Investments [Line Items]
Debt securities, available-for-sale, cost (in dollars)	67,118
Debt Securities, Fair Value	$ 67,424	$ 52,060