Investment in Securities (Schedule of Amortized Cost and Fair Value of Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Amortized Cost, Due in 1 year or less	$ 15,436
Amortized Cost, Due after 1 year through 5 years	72,338
Amortized Cost, Due after 5 years through 10 years	128,561
Amortized Cost, Due after 10 years	52,271
Amortized Cost, Total	268,606
Fair Value, Due in 1 year or less	15,627
Fair Value, Due after 1 year through 5 years	76,717
Fair Value, Due after 5 years through 10 years	131,142
Fair Value, Due after 10 years	52,942
Fair Value, Total	$ 276,428	$ 341,935