Shareholders' Equity - Accelerated Share Repurchases (Details) - 2021 Repurchase Program - USD ($) $ / shares in Units, shares in Millions, $ in Billions	Jan. 04, 2024	Jan. 04, 2023	Jan. 04, 2022	Feb. 28, 2023	Feb. 28, 2022
Morgan Stanley | Subsequent Event
Equity, Class of Treasury Stock [Line Items]
ASR agreement, amount	$ 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
Share price (in dollars per share)	$ 81.19
ASR, maximum amount of shares received or delivered	73.9
ASR, shares to be received at the end of program as a percent of notional amount	15.00%
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
Share price (in dollars per share)		$ 92.19
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 Contracts
Equity, Class of Treasury Stock [Line Items]
Forward contract, notional amount		$ 0.4
Barclays Bank
Equity, Class of Treasury Stock [Line Items]
ASR agreement, amount			$ 1.5		$ 1.5
Payments for ASR, amount			$ 1.5
ASR percent of notional amount received in shares			80.00%
Shares repurchased under ASR agreement (in shares)			11.6		2.7
Share price (in dollars per share)			$ 103.34
Transfer of shares to treasury stock value			$ 1.2
ASR, shares to be received at the end of program as a percent of notional amount					20.00%
Barclays Bank | Forward Contracts
Equity, Class of Treasury Stock [Line Items]
Forward contract, notional amount			$ 0.3