Acquisition - Schedule of Preliminary Purchase Price of Assets Acquired and Liabilities Assumed (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014	Apr. 03, 2014	Dec. 31, 2013
ASSETS
Goodwill	$ 49,600,000	$ 28,176,000		$ 19,748,000
Total assets purchased	148,200,000
Deposits
Total liabilities assumed	$ 122,800,000
Summit [Member]
ASSETS
Cash and due from banks			$ 15,161,000
Total loans			124,081,000
Premises and equipment, net			2,548,000
FRB and FHLB stock			2,136,000
Goodwill			8,428,000
Core deposit intangible			822,000
Interest receivable			347,000
Cash value of life insurance			2,185,000
Other assets			2,877,000
Total assets purchased			158,585,000
Deposits
Non-interest bearing			27,274,000
NOW accounts			16,332,000
Savings and money market			35,045,000
Certificates of deposits			42,368,000
Total deposits			121,019,000
Borrowings			16,990,000
Interest payable			52,000
Other liabilities			599,000
Total liabilities assumed			138,660,000
Summit [Member] | Residential Mortgage [Member]
ASSETS
Total loans			43,448,000
Summit [Member] | Commercial [Member]
ASSETS
Total loans			70,441,000
Summit [Member] | Consumer [Member]
ASSETS
Total loans			$ 10,192,000