Adoption of New Revenue Recognition Standard - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Equipment sale performance obligation		$ 50
Increase to Sales		933	$ 936
Decrease to service revenue		(1,431)	$ (1,442)
Transition asset		153
Increase to retained earnings	[1]	117
Contract liabilities		$ 87		$ 91
Contract liability amortization period		30 months
Incremental direct costs of obtaining a contract		$ 17
Amortization of incremental direct costs of obtaining a contract		24
Deferred incremental direct costs net of accumulated amortization		$ 179
Deferred incremental direct costs, amortization period		4 years
Contract Fulfillment Costs and Inducements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Incremental direct costs of obtaining a contract		$ 10
ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase to Sales		9
Decrease to service revenue		9
Increase to retained earnings		$ 117

[1] Refer to Note 3 - Adoption of New Revenue Recognition Standard for additional information.