Loans and Allowance for Loan Losses - Schedule of Activity of Purchased Impaired Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	$ 42,032	$ 55,419
Allowance for loan losses	(428)	(278)
Carrying amount, net of allowance	41,604	55,141
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	622	850
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	22,287	32,774
Residential [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	12,578	13,580
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Purchased impaired loans	$ 6,545	$ 8,215