Commitments and Letters of Credit - Notional Amount of Commitments and Letter of Credit Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Commitments to extend credit [Member]
Loss Contingencies [Line Items]
Financial instrument of credit risk	$ 1,571,987	$ 1,506,618
Financial standby letters of credit [Member]
Loss Contingencies [Line Items]
Financial instrument of credit risk	38,121	47,185
Performance standby letters of credit [Member]
Loss Contingencies [Line Items]
Financial instrument of credit risk	32,441	69,240
Commercial letters of credit [Member]
Loss Contingencies [Line Items]
Financial instrument of credit risk	$ 0	$ 685