Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 4,288	$ 5,021	$ 13,344	$ 14,762
United States
Disaggregation of Revenue [Line Items]
Revenues	1,290	1,843	4,665	5,500
United Kingdom
Disaggregation of Revenue [Line Items]
Revenues	607	707	1,759	2,100
Other Europe
Disaggregation of Revenue [Line Items]
Revenues	1,335	1,329	3,784	3,819
Australia
Disaggregation of Revenue [Line Items]
Revenues	377	380	1,128	1,119
Other International
Disaggregation of Revenue [Line Items]
Revenues	$ 679	$ 762	$ 2,008	$ 2,224