Investment Securities Available for Sale (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Market Value	$ 352,811	$ 346,043
U.S. Government securities
Schedule of Available-for-sale Securities [Line Items]
Under 1 Year	0
1 Year up to 5 Years	32,423
More than 5 Years	0
Market Value	32,423
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Under 1 Year	7,497
1 Year up to 5 Years	43,181
More than 5 Years	10,992
Market Value	61,670
U.S. mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Under 1 Year	963
1 Year up to 5 Years	5,665
More than 5 Years	179
Market Value	6,807
Commercial mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Under 1 Year	3,895
1 Year up to 5 Years	6,785
More than 5 Years	6,083
Market Value	16,763
U.S. asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Under 1 Year	3,521
1 Year up to 5 Years	10,684
More than 5 Years	1,833
Market Value	16,038
Index-linked U.S. bonds
Schedule of Available-for-sale Securities [Line Items]
Under 1 Year	0
1 Year up to 5 Years	2,115
More than 5 Years	0
Market Value	2,115
Marketable debt securities
Schedule of Available-for-sale Securities [Line Items]
Under 1 Year	15,876
1 Year up to 5 Years	100,853
More than 5 Years	19,087
Market Value	$ 135,816