Restructuring and Transaction Costs (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring and transaction costs	$ 189
Reduction of workforce [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and transaction costs	143
Expense associated with accelerated awards	21
Reduction Of Workforce | Defined Benefit Settlements [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and transaction costs	37
Transaction Costs [Member]
Restructuring Cost And Reserve [Line Items]
Underwriting, bank, legal and accounting fees	$ 46