Deposits (Additional Information About Corporation's Deposits) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deposits [Abstract]
Deposits from the Certificate of Deposit Account Registry Service (CDARS)	$ 0	$ 2,615
Deposits from the Promontory Interfinancial Network Insured Cash Sweep Service (acquired in the acquisition of WNB)	0	7,440
Deposits from foreign sources (primarily Mexico)	776,003	747,008
Deposits not covered by deposit insurance	12,889,047	11,953,367
Deposits from certain directors, executive officers and their affiliates	$ 199,969	$ 218,095