Investment Securities Summary of Amortized Cost and Fair Values of Corporate Debt Securities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Available-for-sale Securities, Debt Securities	$ 2,556,248
Corporate Debt Securities Issued by Financial Institutions [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	130,319	134,547
Available-for-sale Securities, Debt Securities	120,770	122,232
Single-issuer Trust Preferred Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	83,899	91,257
Available-for-sale Securities, Debt Securities	74,365	81,789
Subordinated Debt [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	40,184	34,995
Available-for-sale Securities, Debt Securities	41,296	35,915
Pooled Trust Preferred Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	6,236	8,295
Available-for-sale Securities, Debt Securities	5,109	4,528
Other Corporate Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	2,536	2,554
Available-for-sale Securities, Debt Securities	2,536	2,554
Corporate Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	132,855	137,101
Available-for-sale Securities, Debt Securities	$ 123,306	$ 124,786

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

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+ Details