Commitments and Contingent Liabilities - Summary of Financial Instruments with Off-Balance-Sheet Risks (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]
Loan commitments	$ 937,221	$ 945,270
Stand-by letters of credit	$ 63,734	$ 61,262