Investment Securities Held-to-Maturity (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Company's securities held-to-maturity
Within one year, Amortized Cost	$ 4,310
After one but within five years, Amortized Cost	205,007
After five but within ten years, Amortized Cost	50,956
More than ten years, Amortized Cost	272
Total, Amortized Cost	260,545
Within one year, Fair Value	4,361
After one but within five years, Fair Value	209,438
After five but within ten years, Fair Value	51,967
More than ten years, Fair Value	281
Total, Fair Value	$ 266,047