Collateralized Transactions (Customer Margin Lending and Other) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Collateralized Transactions
Net customer receivables representing margin loans	$ 34,382	$ 32,112

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