Commitments and Contingencies (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Contractual amount net of risk participations	$ 83,000
Accrued liabilities related to mortgage repurchase claims	2,300	$ 3,200
Guarantee Obligations [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	8,845,199
Letters of Credit [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	150,948
Commitments to Fund Commercial Real Estate, Construction, and Land Development Loans [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	1,394,162
Unused Credit Card Lines [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	1,103,431
Commitments under Home Equity Lines of Credit [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	1,096,052
Commitments to Fund Commercial and Industrial Loans [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	4,792,834
Other Loan Commitments [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	$ 307,772