Investment Securities (Details 2) (USD $) In Thousands	Jun. 30, 2011
Amortized Cost, Available-for-Sale
Due in One Year or Less	$ 256,617
Due After One Year Through Five Years	746,982
Due After Five Years Through Ten Years	80,904
Due After Ten Years	103,065
Total	1,187,568
Fair Value, Available-for-Sale
Due in One Year or Less	257,384
Due After One Year Through Five Years	754,351
Due After Five Years Through Ten Years	82,104
Due After Ten Years	103,795
Total	1,197,634
Investment Securities, Held-to-Maturity:
Amortized Cost, Due After One Year Through Five Years	179,489
Fair Value, Due After One Year Through Five Years	$ 183,068