Investment Securities Summary of Amortized Cost and Fair Values of Corporate Debt Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	$ 2,772,533
Corporate Debt Securities Issued by Financial Institutions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	105,816	109,650
Available-for-sale Securities, Debt Securities	104,978	110,330
Single-issuer Trust Preferred Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	54,699	56,834
Available-for-sale Securities, Debt Securities	49,222	51,656
Subordinated Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	47,344	47,286
Available-for-sale Securities, Debt Securities	50,365	51,747
Pooled Trust Preferred Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	3,773	5,530
Available-for-sale Securities, Debt Securities	5,391	6,927
Other Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,499	2,512
Available-for-sale Securities, Debt Securities	2,499	2,512
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	108,315	112,162
Available-for-sale Securities, Debt Securities	$ 107,477	$ 112,842

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

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+ Details