Other Borrowings - Summary of Balances of Other Borrowings (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Collateralized borrowing, fixed rate, as of September 30, 2017 of 1.11% & 0.05%, payable on October 2, 2017	$ 12,993,000	$ 17,493,000
Total other borrowings	98,730,000	17,493,000
1.11% Fixed Rate FHLB Collateralized Borrowings [Member]
Debt Instrument [Line Items]
Collateralized borrowing, fixed rate, as of September 30, 2017 of 1.11% & 0.05%, payable on October 2, 2017	85,737,000
0.05% Fixed Rate Collateralized Borrowings [Member]
Debt Instrument [Line Items]
Collateralized borrowing, fixed rate, as of September 30, 2017 of 1.11% & 0.05%, payable on October 2, 2017	$ 12,993,000	$ 17,493,000