Securities (Schedule of Contractual Maturities of Investment Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012
Available-for-sale Securities [Abstract]
Due within one year, Amortized Cost	$ 22,442
Due after one year through five years, Amortized Cost	78,072
Due after five years through ten years, Amortized Cost	190,442
Due after ten years, Amortized Cost	667,044
Total investment securities available-for-sale, Amortized Cost	958,000
Due within one year, Fair Value	22,749
Due after one year through five years, Fair Value	80,627
Due after five years through ten years, Fair Value	199,359
Due after ten years, Fair Value	693,153
Total investment securities available-for-sale, Fair Value	$ 995,888

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This item represents debt securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature after five years and through ten years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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