Investment in Securities (Schedule of Amortized Cost and Fair Value of Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Investment in Securities [Abstract]
Amortized Cost, Due in 1 year or less	$ 29,318
Amortized Cost, Due after 1 year through 5 years	88,584
Amortized Cost, Due after 5 years through 10 years	130,196
Amortized Cost, Due after 10 years	60,093
Amortized Cost, Total	308,191
Fair Value, Due in 1 year or less	29,603
Fair Value, Due after 1 year through 5 years	92,912
Fair Value, Due after 5 years through 10 years	136,890
Fair Value, Due after 10 years	63,222
Fair Value, Total	$ 322,627	$ 356,141