Segment and Geographic Information - Geographic PPE (Details) - USD ($) $ in Millions	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Property and Equipment, net	$ 3,547	$ 3,179	$ 3,363
United States
Segment Reporting Information [Line Items]
Property and Equipment, net	1,621	1,352	1,270
United Kingdom
Segment Reporting Information [Line Items]
Property and Equipment, net	493	512	535
Australia
Segment Reporting Information [Line Items]
Property and Equipment, net	134	144	191
Other Europe
Segment Reporting Information [Line Items]
Property and Equipment, net	757	553	465
Other International
Segment Reporting Information [Line Items]
Property and Equipment, net	$ 542	$ 618	$ 902