Borrowed Funds - Schedule of Repayment of Long-Term Borrowings for Securities Sold Under Agreements to Repurchase (Detail) - Long-term borrowings - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
2022	$ 50,000
Total long-term securities sold under agreements to repurchase	$ 50,000	$ 100,000