Acquired SJB Assets and FDIC Loss Sharing Asset - Summary of Gross PCI Loans by Internal Risk Ratings by Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross PCI loans	$ 76,022		$ 110,746
PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross PCI loans	76,022	$ 93,712	$ 110,746
PCI Loans [Member] | Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross PCI loans	60,181	76,401
PCI Loans [Member] | Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross PCI loans	10,255	11,142
PCI Loans [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross PCI loans	5,586	6,169
PCI Loans [Member] | Doubtful & Loss [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross PCI loans	$ 0	$ 0