Restructuring Narrative (Details) - 2017 Plan $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($) job_elimination
Restructuring Cost and Reserve [Line Items]
Expected total cost	$ 750	$ 750
Number of positions eliminated to date | job_elimination		2,125
Costs incurred	102	$ 401
Workforce reduction
Restructuring Cost and Reserve [Line Items]
Expected total cost	303	303
Costs incurred	52	257
Technology rationalization
Restructuring Cost and Reserve [Line Items]
Expected total cost	146	146
Costs incurred	12	22
Lease consolidation
Restructuring Cost and Reserve [Line Items]
Expected total cost	80	80
Costs incurred	4	8
Asset impairments
Restructuring Cost and Reserve [Line Items]
Expected total cost	40	40
Costs incurred	2	26
Other Restructuring
Restructuring Cost and Reserve [Line Items]
Expected total cost	181	181
Costs incurred	32	88
Non-cash charges for asset impairments and lease consolidations
Restructuring Cost and Reserve [Line Items]
Expected total cost	$ 50	$ 50
Minimum
Restructuring Cost and Reserve [Line Items]
Expected number of positions eliminated | job_elimination		2,400
Maximum
Restructuring Cost and Reserve [Line Items]
Expected number of positions eliminated | job_elimination		2,850