Financial Instruments with Off-Balance-Sheet Risk - Schedule of Financial Instruments with Off-Balance-Sheet Risk (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Concentration Risk [Line Items]
Financial instruments whose contract amounts represent credit risk	$ 604,281
Unfunded Lines of Credit [Member]
Concentration Risk [Line Items]
Financial instruments whose contract amounts represent credit risk	444,687
Unfunded Commitments to Extend Credit [Member]
Concentration Risk [Line Items]
Financial instruments whose contract amounts represent credit risk	128,293
Standby Letters of Credit [Member]
Concentration Risk [Line Items]
Financial instruments whose contract amounts represent credit risk	$ 31,301