Cash and Due from Banks - Additional Information (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Cash and Due from Banks [Abstract]
Reserve balance of cash and due from banks	$ 0	$ 0

Amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers).

No definition available.

Name:	us-gaap_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant