Acquisitions/Divestitures - Divestitures (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2019	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2019
Select Standalone Cloud and Cognitive Software Products
Divestitures
Consideration	$ 1,775			$ 1,775
Contingent consideration included in total	$ 150			150
Cash consideration received		$ 164		812
Contingent consideration received			$ 40
Remaining consideration to be received		648
Pre-tax gain on sale of business		625
Cash remitted		(139)
Cash expected to be remitted in 2021		$ (185)
Period after closing to receive outstanding contingent consideration	24 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
Sales Performance Management Offerings
Divestitures
Cash consideration received					$ 230
Pre-tax gain on sale of business					$ 136