Short-Term and Other Borrowings - Summary of Securities Pledged as Collateral Under Repurchase Agreements (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Offsetting Liabilities [Line Items]
Total securities pledged	$ 23,331	$ 28,914
Gross amount of recognized liabilities for repurchase agreements	23,331	28,914
Amounts related to agreements not included in offsetting disclosures above	0	0
U.S.Treasury Securities [Member]
Offsetting Liabilities [Line Items]
Total securities pledged	7,656	899
Obligations of U.S. Government Agencies [Member]
Offsetting Liabilities [Line Items]
Total securities pledged	$ 15,675	$ 28,015