Note Commitments and Contingencies (Financial instruments with off-Balance Sheet credit risk) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitments To Extend Credit | Credit card
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Unused Commitments To Extend Credit	$ 4,530,162	$ 4,468,481
Commitments To Extend Credit | Commercial and construction lines of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Unused Commitments To Extend Credit	2,806,405	2,751,390
Commitments To Extend Credit | Other consumer unused credit commitments
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Unused Commitments To Extend Credit	258,884	254,491
Commercial Letters of Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Unused Commitments To Extend Credit	1,303	2,695
Standby Letters of Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Unused Commitments To Extend Credit	79,200	26,479
Commitments to originate or fund mortgage loans
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Unused Commitments To Extend Credit	$ 22,884	$ 22,629