Loans Receivable and Allowance for Loan Losses - Narrative (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Loan Allowance Commitment	Dec. 31, 2014 USD ($) Loan Allowance Commitment	Dec. 31, 2013 USD ($) Loan Allowance Commitment
Financing Receivable, Modifications [Line Items]
Covered loans outstanding	$ 13,800	$ 42,200
Clawback liability payment date	45 days
Clawback liability	$ 2,300
Expected FDIC receivable	200
Clawback liability, net	2,100
Troubled debt restructurings loans	$ 11,400	$ 5,000	$ 4,600
Minimum performance requirement (months)	6 months
Sustained performance period (months)	6 months
Commitments to lend additional funds to debtors | Commitment	0	0	0
Recorded investment of loans determined to be TDR	$ 7,500	$ 1,100	$ 1,200
Number of TDR loans | Loan	36	6	5
Recorded investment	$ 2,500	$ 400	$ 400
Recorded investment, portion subject to a cash reserve	$ 1,800
TDR modification (allowance) | Allowance	3	0	0
Available funds for reimbursement	$ 1,200	$ 3,000
Residential Real Estate
Financing Receivable, Modifications [Line Items]
Other real estate owned	1,200
Foreclosure loans	$ 600
Commercial and industrial (including owner occupied commercial real estate)
Financing Receivable, Modifications [Line Items]
TDR modification (allowance) | Allowance	2
Allowance for TDR modification	$ 200
Commercial real estate non-owner occupied
Financing Receivable, Modifications [Line Items]
TDR modification (allowance) | Allowance	1
Allowance for TDR modification	$ 100
Troubled Debt Restructurings
Financing Receivable, Modifications [Line Items]
Sustained performance period (months)	9 months