Commitments - Extended Warranty Liability, Contract Liability (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Movement in deferred income
Amortization of deferred revenue	$ (3,500)
Current portion	13,059	$ 13,059	$ 11,493	$ 11,552
Noncurrent portion	3,852	3,852	$ 3,758	$ 3,746
Extended Warranty
Movement in deferred income
Beginning Balance		566
Revenue deferred for new extended warranty contracts		46
Amortization of deferred revenue		(69)
Other		5
Ending Balance	548	548
Current portion	260	260
Noncurrent portion	$ 288	$ 288