Restructuring and Asset Impairment Charges (Schedule of Restructuring Charges) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Charged to Costs and Expenses	$ 0	$ 6	$ 1	$ 11
Restructuring costs incurred to date	17		17
Branch closure charges
Restructuring Reserve [Roll Forward]
Restructuring costs incurred to date	8		8
Severance and other
Restructuring Reserve [Roll Forward]
Restructuring costs incurred to date	9		9
2020-2021 Cost Savings Restructuring Program
Restructuring Reserve [Roll Forward]
Beginning Reserve Balance			5
Charged to Costs and Expenses			1
Payments and Other			(5)
Ending Reserve Balance	1		1
2020-2021 Cost Savings Restructuring Program | Branch closure charges
Restructuring Reserve [Roll Forward]
Beginning Reserve Balance			3
Charged to Costs and Expenses			0
Payments and Other			(2)
Ending Reserve Balance	1		1
2020-2021 Cost Savings Restructuring Program | Severance and other
Restructuring Reserve [Roll Forward]
Beginning Reserve Balance			2
Charged to Costs and Expenses			1
Payments and Other			(3)
Ending Reserve Balance	$ 0		$ 0