Restructuring and Asset Impairment Charges - Summary of Restructuring Charges (Details) - Strategic Growth Initiative Plan - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Severance and employee-related costs, net	$ 6	$ 20
Exit-related costs	45	69
Asset impairments and accelerated depreciation and amortization	2	22
Net restructuring charges recognized	53	111
U.S. Pharmaceutical and Specialty Solutions
Restructuring Cost and Reserve [Line Items]
Severance and employee-related costs, net	0	3
Exit-related costs	5	6
Asset impairments and accelerated depreciation and amortization	0	4
Net restructuring charges recognized	5	13
Medical-Surgical Solutions
Restructuring Cost and Reserve [Line Items]
Severance and employee-related costs, net	0	10
Exit-related costs	5	7
Asset impairments and accelerated depreciation and amortization	1	1
Net restructuring charges recognized	6	18
Other
Restructuring Cost and Reserve [Line Items]
Severance and employee-related costs, net	6	7
Exit-related costs	35	56
Asset impairments and accelerated depreciation and amortization	1	17
Net restructuring charges recognized	$ 42	$ 80