Deposits (Additional Information About Corporation's Deposits) (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deposits [Abstract]
Deposits from the Certificate of Deposit Account Registry Service (CDARS)	$ 2,615	$ 22,229
Deposits from the Promontory Interfinancial Network Insured Cash Sweep Service (acquired in the acquisition of WNB)	7,440	148,665
Deposits from foreign sources (primarily Mexico)	747,008	744,295
Deposits not covered by deposit insurance	11,953,367	12,056,180
Deposits from certain directors, executive officers and their affiliates	$ 218,095	$ 176,821