Investment Securities Summary of Amortized Cost and Fair Values of Corporate Debt Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	$ 2,455,464
Corporate Debt Securities Issued by Financial Institutions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	97,763	97,883
Available-for-sale Securities, Debt Securities	97,967	96,164
Single-issuer Trust Preferred Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Trust Preferred Securities Below Investment Grade	22
Available-for-sale Debt Securities, Amortized Cost Basis	47,502	47,481
Available-for-sale Securities, Debt Securities	41,879	40,531
Subordinated Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	47,436	47,405
Available-for-sale Securities, Debt Securities	50,429	50,327
Pooled Trust Preferred Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Trust Preferred Securities Below Investment Grade	8
Available-for-sale Debt Securities, Amortized Cost Basis	2,825	2,997
Available-for-sale Securities, Debt Securities	5,659	5,306
Other Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,585	2,585
Available-for-sale Securities, Debt Securities	2,585	2,585
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	100,348	100,468
Available-for-sale Securities, Debt Securities	$ 100,552	$ 98,749