Commitments and Contingencies (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Guarantor Obligations [Line Items]
FDIC Indemnification Asset	$ 9,276	$ 5,808	$ 28,701	$ 45,140	$ 49,959	$ 93,397
FDIC loss share payable	124,038		116,535
Commitments to Extend Credit
Guarantor Obligations [Line Items]
Unused Commitments to Extend Credit	7,760,000		7,190,000
Qualified Affordable Housing Project Investments, Commitment	32,000		16,800
Standby Letters of Credit
Guarantor Obligations [Line Items]
Guarantor obligations amount	$ 85,200		77,400
Recourse Obligation on Mortgage Loans Sold
Guarantor Obligations [Line Items]
Recourse Period, Maximum1	120 days
Obligation to Repurchase Receivables Sold
Guarantor Obligations [Line Items]
Reserve for estimated losses arising from repurchase of loans	$ 3,100		$ 3,200