Collateralized Transactions - Securities Segregated for Regulatory Purposes (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Collateralized Agreements [Abstract]
Segregated securities	$ 34,106	$ 25,061

Securities deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations.

No definition available.

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