Restructuring Charges (Narrative) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($) restructuring_program	Dec. 31, 2015 USD ($) restructuring_program	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charge		$ 6	$ (1)	$ 12
Closed Restructuring Programs
Restructuring Cost and Reserve [Line Items]
Number of restructuring programs | restructuring_program	2	2
Restructuring charges incurred to date	$ 216	$ 216
Restructuring charge		2	(1)	12
Closed Restructuring Programs | Branch closure charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred to date	150	150
Restructuring charge		2	(1)	10
Closed Restructuring Programs | Severance costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred to date	66	66
Restructuring charge		0	$ 0	$ 2
2015-2016 Cost Savings Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring charge	$ 4	4
2015-2016 Cost Savings Restructuring Program | Branch closure charges
Restructuring Cost and Reserve [Line Items]
Restructuring charge		0
2015-2016 Cost Savings Restructuring Program | Severance costs
Restructuring Cost and Reserve [Line Items]
Restructuring charge		$ 4