Shareholders' Equity - Accelerated Share Repurchases (Details) - 2021 Repurchase Program - USD ($) shares in Millions, $ in Billions	Jan. 04, 2024	Jan. 04, 2023	Mar. 31, 2024	Feb. 28, 2023
Morgan Stanley & Co. LLC
Equity, Class of Treasury Stock [Line Items]
ASR agreement, amount	$ 3.0		$ 3.0
Payments for ASR, amount	$ 3.0
ASR percent of notional amount received in shares	85.00%
Shares repurchased under ASR agreement (in shares)	31.4		8.3
Transfer of shares to treasury stock value	$ 2.6
ASR, shares to be received at the end of program as a percent of notional amount			15.00%
Morgan Stanley & Co. LLC | Forward contract
Equity, Class of Treasury Stock [Line Items]
Forward contract, notional amount	$ 0.4
Citibank, N.A.
Equity, Class of Treasury Stock [Line Items]
ASR agreement, amount		$ 2.0		$ 2.0
Payments for ASR, amount		$ 2.0
ASR percent of notional amount received in shares		80.00%
Shares repurchased under ASR agreement (in shares)		17.4		5.4
Transfer of shares to treasury stock value		$ 1.6
ASR, shares to be received at the end of program as a percent of notional amount				20.00%
Citibank, N.A. | Forward contract
Equity, Class of Treasury Stock [Line Items]
Forward contract, notional amount		$ 0.4