Restructuring Costs (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Estimated remaining costs	$ 475
Restructuring and related cost, cost incurred to date	441
Costs incurred in other restructuring	301	$ 427
Risk and Insurance Services
Restructuring Cost and Reserve [Line Items]
Costs incurred in other restructuring	177	254
Exit costs		$ 89
Severance and Lease Exit Charges
Restructuring Cost and Reserve [Line Items]
Costs incurred in other restructuring	$ 222