Restructuring Costs (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended
	Mar. 31, 2023	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Costs incurred		$ 53	$ 30
Severance and Lease Exit Charges
Restructuring Cost and Reserve [Line Items]
Costs incurred	$ 243	24
Minimum
Restructuring Cost and Reserve [Line Items]
Estimated remaining costs				$ 375
Maximum
Restructuring Cost and Reserve [Line Items]
Estimated remaining costs				$ 400
Corporate
Restructuring Cost and Reserve [Line Items]
Costs incurred		12	8
Risk and Insurance Services
Restructuring Cost and Reserve [Line Items]
Costs incurred		32	16
Consulting
Restructuring Cost and Reserve [Line Items]
Costs incurred		$ 9	$ 6