Investment Securities Summary of Amortized Cost and Fair Values of Corporate Debt Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	$ 2,687,957
Corporate Debt Securities Issued by Financial Institutions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	109,708	109,650
Available-for-sale Securities, Debt Securities	112,531	110,330
Single-issuer Trust Preferred Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	56,863	56,834
Available-for-sale Securities, Debt Securities	52,523	51,656
Subordinated Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	47,315	47,286
Available-for-sale Securities, Debt Securities	51,652	51,747
Pooled Trust Preferred Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	5,530	5,530
Available-for-sale Securities, Debt Securities	8,356	6,927
Other Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,513	2,512
Available-for-sale Securities, Debt Securities	2,513	2,512
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	112,221	112,162
Available-for-sale Securities, Debt Securities	$ 115,044	$ 112,842

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

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