Goodwill and Intangible Assets, Net - Goodwill Narrative (Details) $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($) reporting_unit	Mar. 31, 2018 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($) reporting_unit	Mar. 31, 2018 USD ($)
Goodwill [Line Items]
Goodwill impairment charge					$ 2	$ 1,797	$ 1,738
Number of reporting units | reporting_unit						2
European Pharmaceutical Solutions
Goodwill [Line Items]
Goodwill impairment charge	$ 1,200		$ 570		0	$ 1,776	$ 1,300
Number of reporting units | reporting_unit			2
Accumulated goodwill impairment loss	3,100				3,100	3,100
Other
Goodwill [Line Items]
Goodwill impairment charge					2	21
Accumulated goodwill impairment loss	476				$ 478	476
RP | European Pharmaceutical Solutions
Goodwill [Line Items]
Tax charged related to impairment						$ 20
Goodwill impairment charge	$ 465		$ 251
Rexall Health | Other
Goodwill [Line Items]
Goodwill impairment charge		$ 21		$ 455