Restructuring Charges (Narrative) (Details) $ in Millions	Dec. 31, 2016 USD ($) restructuring_program
Closed Restructuring Programs
Restructuring Cost and Reserve [Line Items]
Number of restructuring programs | restructuring_program	2
Restructuring charges incurred to date	$ 216
Closed Restructuring Programs | Branch closure charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred to date	150
Closed Restructuring Programs | Severance costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred to date	66
2015-2016 Cost Savings Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred to date	18
2015-2016 Cost Savings Restructuring Program | Branch closure charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred to date	10
2015-2016 Cost Savings Restructuring Program | Severance costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred to date	$ 8