Collateralized Transactions - Customer Margin Lending (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Collateralized Agreements [Abstract]
Customer receivables representing margin loans	$ 26,888	$ 26,225

Receivables generated from margin lending activities that are collateralized by customer-owned securities held by the entity.

No definition available.

Name:	ms_MarginLendingReceivables
Namespace Prefix:	ms_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant