Commitments, Guarantees and Contingencies - Narrative (Details) - Dec. 31, 2021 - Pending Litigation € in Millions, $ in Millions	USD ($)	EUR (€)
Financial Guaranty Insurance Company v. Morgan Stanley ABS Capital I Inc. et al. (Trust 2007-NC4)
Loss Contingencies
Face amount of debt instrument	$ 876
Deutsche Bank National Trust Company solely in its capacity as Trustee of the Morgan Stanley ABS Capital I Inc. Trust 2007-NC4 v. Morgan Stanley Mortgage Capital Holdings LLC as Successor-by-Merger to Morgan Stanley Mortgage Capital Inc., and Morgan Stanley ABS Capital I Inc. | Maximum
Loss Contingencies
Estimate of possible loss	277
US Bank National Association, solely in its capacity as Trustee of the Morgan Stanley Mortgage Loan Trust 2007-2AX (MSM 2007-2AX) v. Morgan Stanley Mortgage Capital Holdings LLC, as Successor-by-Merger to Morgan Stanley Mortgage Capital Inc. and GreenPoint Mortgage Funding, Inc.
Loss Contingencies
Face amount of debt instrument	1,050
Case Number 15/3637 and Case Number 15/4353
Loss Contingencies
Withholding tax credit set-off	$ 141	€ 124