Employee Benefits - Schedule of expense recognized in Compensation and benefit in the Consolidated Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expense recognized for defined contribution savings plans	$ 155	$ 164	$ 168
U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expense recognized for defined contribution savings plans	87	98	98
U.K.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expense recognized for defined contribution savings plans	42	41	45
Netherlands and Canada
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expense recognized for defined contribution savings plans	$ 26	$ 25	$ 25