Share-Based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Shares
Beginning balance (in shares)	3
Granted (in shares)	0
Cancelled (in shares)	0
Exercised (in shares)	(1)
Ending balance (in shares)	2	3
Weighted- Average Exercise Price
Beginning balance (in dollars per share)	$ 166.72
Granted (in dollars per share)	0
Cancelled (in dollars per share)	171.39
Exercised (in dollars per share)	113.34
Ending balance (in dollars per share)	$ 180.48	$ 166.72
Weighted- Average Remaining Contractual Term (Years)
Stock options outstanding, remaining contractual term	3 years	3 years
Stock options outstanding, aggregate intrinsic value	$ 1	$ 4
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract]
Stock options vested and expected to vest (in shares)	2
Stock options vested and exercisable (in shares)	2
Stock options vested and expected to vest, weighted average exercise price (in dollars per share)	$ 180.52
Stock options vested and exercisable, weighted average exercise price (in dollars per share)	$ 189.28
Stock options vested and expected to vest, weighted average remaining contractual term	3 years
Stock options vested and exercisable, weighted average remaining contractual term	2 years
Stock options vested and expected to vest, aggregate intrinsic value	$ 1
Stock options vested and exercisable, aggregate intrinsic value	$ 1