Investment Securities Summary of Amortized Cost and Fair Values of Corporate Debt Securities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Available-for-sale Securities, Debt Securities	$ 2,671,162
Corporate Debt Securities Issued by Financial Institutions [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	109,650	130,319
Available-for-sale Securities, Debt Securities	110,330	120,770
Single-issuer Trust Preferred Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	56,834	83,899
Available-for-sale Securities, Debt Securities	51,656	74,365
Subordinated Debt [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	47,286	40,184
Available-for-sale Securities, Debt Securities	51,747	41,296
Pooled Trust Preferred Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	5,530	6,236
Available-for-sale Securities, Debt Securities	6,927	5,109
Other Corporate Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	2,512	2,536
Available-for-sale Securities, Debt Securities	2,512	2,536
Corporate Debt Securities [Member]
Available-for-sale Debt Securities, Amortized Cost Basis	112,162	132,855
Available-for-sale Securities, Debt Securities	$ 112,842	$ 123,306

Amount of debt securities categorized neither as held-to-maturity nor trading.

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