Investment Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012
Investment Securities Available-for-Sale:
Due in one year or less, Amortized Cost	$ 123,976
Due after one year through five years, Amortized Cost	415,814
Due after five years through ten years, Amortized Cost	54,967
Due after ten years, Amortized Cost	73,469
Preferred stock, Amortized Cost	6,144
Total Available-for-sale Securities, Debt Maturities, Amortized Cost	674,370
Due in one year or less , Fair Value	124,424
Due after one year through five years, Fair Value	418,132
Due after five years through ten years, Fair Value	57,144
Due after ten years, Fair Value	74,330
Preferred stock, Fair Value	6,201
Total Available-for-sale securities, Debt maturities, Fair Value	680,231
Investment Securities Held-to-Maturity:
Due in one year or less, Amortized Cost	35,811
Due after one year through five years, Amortized Cost	92,961
Due after five years through ten years, Amortized Cost	54,792
Due after ten years, Amortized Cost	29,470
Total Held-to-maturity securities, Debt maturities, Amortized Cost	213,034
Due in one year or less , Fair Value	35,757
Due after one year through five years, Fair Value	94,725
Due after five years through ten years, Fair Value	58,452
Due after ten years, Fair Value	24,918
Total Held-to-maturity securities, Debt maturities, Fair Value	$ 213,852