Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended			132 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Loss Contingencies [Line Items]
Loan commitments and letters of credit	$ 15,000			$ 15,000
Contractual amount net of risk participations	66,000			66,000
Operating Leases, Future Minimum Payments Due [Abstract]
2016	26,263			26,263
2017	25,008			25,008
2018	23,291			23,291
2019	20,707			20,707
2020	20,904			20,904
Thereafter	176,444			176,444
Total	292,617			292,617
Operating leases, rent expense	26,600	$ 25,900	$ 25,600
First lien GSE eligible mortgage loans originated and sold				8,900,000
First and second lien non-GSE eligible mortgage loans originated and sold				3,900,000
Mortgage repurchase claim expense	920	2,000	$ 1,700
Accrued liabilities related to mortgage repurchase claims	3,200	$ 3,200		3,200
Guarantee Obligations [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	8,523,072			8,523,072
Standby and Commercial Letters of Credit [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	166,936			166,936
Commitments to Fund Commercial Real Estate, Construction, and Land Development Loans [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	1,882,130			1,882,130
Unused Credit Card Lines [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	1,055,181			1,055,181
Commitments under Home Equity Lines of Credit [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	1,051,386			1,051,386
Commitments to Fund Commercial and Industrial Loans [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	4,094,809			4,094,809
Other Loan Commitments [Member]
Loss Contingencies [Line Items]
Loan commitments and letters of credit	$ 272,630			$ 272,630