Property, Plant and Equipment (Components of Property Plant and Equipment, Specifically Leased Devices) (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2018	Mar. 31, 2018
Property, Plant and Equipment [Line Items]
Document Period End Date	Jun. 30, 2018
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ (18,418)	$ (17,423)
Property, plant and equipment, net	20,538	19,925
Leased devices [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	10,145	9,592
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(3,932)	(3,580)
Property, plant and equipment, net	$ 6,213	$ 6,012