Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Unpaid Principal Balances and Related Carrying Amounts of Acquired Loans (Detail) - USD ($) $ in Thousands |
Sep. 30, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Outstanding balance | $ 53,684 | $ 62,480 |
| Carrying Amount | 51,247 | 58,633 |
| Credit Impaired Purchased Loans Evaluated Individually for Incurred Credit Losses [Member] | ||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Outstanding balance | 1,496 | 2,672 |
| Carrying Amount | 678 | 713 |
| Other Purchased Loans Evaluated Collectively for Incurred Credit Losses [Member] | ||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Outstanding balance | 52,188 | 59,808 |
| Carrying Amount | $ 50,569 | $ 57,920 |