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Acquisitions/Divestitures - Acquisitions/Divestitures - Purchase Price Allocation (Details) - USD ($) $ in Millions		9 Months Ended
	Jul. 09, 2019	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquisitions
Goodwill		$ 57,951	$ 36,265	$ 36,788
Red Hat, Inc.
Acquisitions
Current assets	$ 3,190
Property, plant, and equipment/noncurrent assets	955
Goodwill	23,102	$ 23,100
Total assets acquired	40,719
Current liabilities	1,378
Noncurrent liabilities	4,262
Total liabilities assumed	5,640
Total purchase price	35,079
Weighted-average useful/amortization life (in yrs.)		10 years 10 months 24 days
Cash and cash equivalents	2,200
Short-term debt	485	$ 50
Red Hat, Inc. \| Completed technology
Acquisitions
Intangible assets	$ 4,571
Weighted-average useful/amortization life (in yrs.)	9 years
Red Hat, Inc. \| Client relationships
Acquisitions
Intangible assets	$ 7,215
Weighted-average useful/amortization life (in yrs.)	10 years
Red Hat, Inc. \| Trademarks
Acquisitions
Intangible assets	$ 1,686
Weighted-average useful/amortization life (in yrs.)	20 years