Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies (Financial Instruments With Off-Balance-Sheet Risk) (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 279,147	$ 248,360
Deferred Standby Letter of Credit Fees [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	2,115	1,942
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 8,246,698	$ 7,955,779