Long-Term Borrowings - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Maximum drawing capacity	$ 525,300,000
FHLB stock holdings	552,500
Advances outstanding	0
Residential Mortgage [Member]
Debt Instrument [Line Items]
Line of credit assets pledged as collateral	669,800,000
Revolving Line of Credit Member]
Debt Instrument [Line Items]
Maximum drawing capacity	$ 10,000,000
Description of variable interest rate	prime rate minus 25 basis points
Line of credit maturity year	2020