Restructuring Charges (Schedule of restructuring charges) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Restructuring Reserve [Roll Forward]
Beginning reserve balance	$ 16
Charged to Costs and Expenses	2	$ 1
Payments and Other	(2)
Ending reserve balance	16
Branch closure charges
Restructuring Reserve [Roll Forward]
Beginning reserve balance	13
Charged to Costs and Expenses	1
Payments and Other	(1)
Ending reserve balance	13
Severance costs
Restructuring Reserve [Roll Forward]
Beginning reserve balance	3
Charged to Costs and Expenses	1
Payments and Other	(1)
Ending reserve balance	3
Closed Restructuring Programs
Restructuring Reserve [Roll Forward]
Beginning reserve balance	13
Charged to Costs and Expenses	0
Payments and Other	(1)
Ending reserve balance	12
Closed Restructuring Programs | Branch closure charges
Restructuring Reserve [Roll Forward]
Beginning reserve balance	13
Charged to Costs and Expenses	0
Payments and Other	(1)
Ending reserve balance	12
Closed Restructuring Programs | Severance costs
Restructuring Reserve [Roll Forward]
Beginning reserve balance	0
Charged to Costs and Expenses	0
Payments and Other	0
Ending reserve balance	0
2015-2016 Cost Savings Restructuring Program
Restructuring Reserve [Roll Forward]
Beginning reserve balance	3
Charged to Costs and Expenses	2
Payments and Other	(1)
Ending reserve balance	4
2015-2016 Cost Savings Restructuring Program | Branch closure charges
Restructuring Reserve [Roll Forward]
Beginning reserve balance	0
Charged to Costs and Expenses	1
Payments and Other	0
Ending reserve balance	1
2015-2016 Cost Savings Restructuring Program | Severance costs
Restructuring Reserve [Roll Forward]
Beginning reserve balance	3
Charged to Costs and Expenses	1
Payments and Other	(1)
Ending reserve balance	$ 3