Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			$ 25	$ 58	$ 58
Cash payments			(43)		(49)
Restructuring charges			511		124
Other			(423)		(108)
Restructuring reserve ending balance	$ 70		70		25
Restructuring and other charges (D)	499	$ 15	511	22
Layoff costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			10	56	56
Cash payments			(40)		(47)
Restructuring charges			39		111
Other			56		(110)
Restructuring reserve ending balance	65		65		10
Restructuring and other charges (D)	(3)	$ (5)	(3)
Other exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			15	2	2
Cash payments			(3)		(2)
Restructuring charges			472		13
Other			(479)		2
Restructuring reserve ending balance	5		5		15
Restructuring and other charges (D)	12		12	$ 4
Employee Severance Cost, Reclassification Of Pension Costs
Restructuring Reserve [Roll Forward]
Other					119
Employee Severance Costs, Credit In Post-Retirement Costs
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)					(28)
Employee Severance, Reversal Of Prior Restructuring
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)					$ (19)
Elimination Of Life Insurance Benefits
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)			(58)
Other, Pension Settlement Cost
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)			4
Other
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)			(2)
Impairment Of Disks
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)	428		428
Loss On Sale Related To Small Additive Business
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)	$ 12		12
Other Exit Costs, Impairment Of Intangibles And Property Plant and Equipment
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)			16
Accelerated Depreciation
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)			2
Other Exit Cost Lease Termination Loss
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)			12
Other Exit Costs, Reclassification Of Lease Exit Costs
Restructuring Reserve [Roll Forward]
Restructuring and other charges (D)			$ (9)