Expenses - Activity Related To Restructuring-Related Accruals (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Restructuring Reserve [Roll Forward]
Balance as of December 31, 2014	$ 71
Additional accruals for Business Operations and Information Technology Transformation program	(8)
Payments and adjustments	(42)
Balance as of September 30, 2015	32
2012 Expense Control Measures
Restructuring Reserve [Roll Forward]
Additional accruals for 2012 expense control measures	11
Employee- Related Costs
Restructuring Reserve [Roll Forward]
Balance as of December 31, 2014	40
Additional accruals for Business Operations and Information Technology Transformation program	(4)
Payments and adjustments	(21)
Balance as of September 30, 2015	15
Employee- Related Costs | 2012 Expense Control Measures
Restructuring Reserve [Roll Forward]
Additional accruals for 2012 expense control measures	0
Real Estate Consolidation
Restructuring Reserve [Roll Forward]
Balance as of December 31, 2014	24
Additional accruals for Business Operations and Information Technology Transformation program	(4)
Payments and adjustments	(8)
Balance as of September 30, 2015	12
Real Estate Consolidation | 2012 Expense Control Measures
Restructuring Reserve [Roll Forward]
Additional accruals for 2012 expense control measures	0
Asset and Other Write-Offs
Restructuring Reserve [Roll Forward]
Balance as of December 31, 2014	7
Additional accruals for Business Operations and Information Technology Transformation program	0
Payments and adjustments	(13)
Balance as of September 30, 2015	5
Asset and Other Write-Offs | 2012 Expense Control Measures
Restructuring Reserve [Roll Forward]
Additional accruals for 2012 expense control measures	$ 11