Financial Guarantees - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Financial Guarantees [Line Items]
Term of standby letters of credit, years	1 year
Notional amount of standby letters of credit	$ 61,600,000	$ 62,600,000
Carrying value of letters of credit	400,000	400,000
Notional amount	661,500,000	$ 761,500,000
Interest Rate Swap [Member]
Financial Guarantees [Line Items]
Notional amount	7,200,000
Interest Rate Swap [Member] | Additional Risk Participation [Member]
Financial Guarantees [Line Items]
Notional amount	$ 10,900,000