Restructuring Narrative (Details) - 2017 Plan $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) job_elimination
Restructuring Cost and Reserve [Line Items]
Expected total cost	$ 750
Number of positions eliminated to date | job_elimination	1,065
Costs incurred	$ 144
Workforce reduction
Restructuring Cost and Reserve [Line Items]
Expected total cost	207
Costs incurred	103
Technology rationalization
Restructuring Cost and Reserve [Line Items]
Expected total cost	146
Costs incurred	3
Lease consolidation
Restructuring Cost and Reserve [Line Items]
Expected total cost	176
Costs incurred	3
Asset impairments
Restructuring Cost and Reserve [Line Items]
Expected total cost	40
Costs incurred	13
Other Restructuring
Restructuring Cost and Reserve [Line Items]
Expected total cost	181
Costs incurred	22
Non-cash charges for asset impairments and lease consolidations
Restructuring Cost and Reserve [Line Items]
Expected total cost	$ 50
Minimum
Restructuring Cost and Reserve [Line Items]
Expected number of positions eliminated | job_elimination	1,600
Maximum
Restructuring Cost and Reserve [Line Items]
Expected number of positions eliminated | job_elimination	1,900