Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due in one year or less	$ 49,977
Amortized Cost, Due after one year through five years	185,036
Amortized Cost, Due after five years through ten years	111,008
Amortized Cost, Amortized Cost Due after ten years	52,806
Debt Maturities, Amortized Cost	450,770
Fair Value, Due in one year or less	50,329
Fair Value, Due after one year through five years	185,525
Fair Value, Due after five years through ten years	109,925
Fair Value, Due after ten years	52,946
Debt securities	450,785	410,095
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Maturities, Amortized Cost	51,943
Debt securities	$ 52,060	$ 27,737