Acquisitions/Divestitures - Divestitures (Details) $ in Millions		3 Months Ended	6 Months Ended	9 Months Ended
	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) entity	Jun. 30, 2019 USD ($) entity	Sep. 30, 2019 entity
Select Standalone Cloud and Cognitive Software Products
Divestitures
Consideration	$ 1,775		$ 1,775
Contingent consideration included in total	150		150
Cash consideration received			812
Contingent consideration received		$ 40
Remaining consideration to be received	$ 813		813
Pre-tax gain on sale of business		$ 72	$ 556
Period after closing for receipt of remaining consideration	12 months
Period to receive outstanding contingent consideration	24 months
Number of divestitures | entity			3	3
Select Standalone Cloud and Cognitive Software Products | Maximum
Divestitures
Initial term for transition services	1 year
Select Marketing Platform and Commerce Offerings | Remaining countries
Divestitures
Period for subsequent closing	12 months
Select Marketing Platform and Commerce Offerings | U.S.
Divestitures
Cash consideration received			$ 240
Remaining consideration to be received	$ 150		$ 150
Period after closing for receipt of remaining consideration	36 months
Select Global Business Services
Divestitures
Number of divestitures | entity		1		1