Restructuring Charges (Schedule of restructuring charges) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Restructuring Reserve [Roll Forward]
Beginning reserve balance	$ 17
Charged to Costs and Expenses	0	$ 2
Payments and Other	(1)
Ending reserve balance	16
Branch closure charges
Restructuring Reserve [Roll Forward]
Beginning reserve balance	16
Charged to Costs and Expenses	0
Payments and Other	0
Ending reserve balance	16
Severance costs
Restructuring Reserve [Roll Forward]
Beginning reserve balance	1
Charged to Costs and Expenses	0
Payments and Other	(1)
Ending reserve balance	$ 0