Share-Based Compensation - Schedule of Data Related to Stock Option Activity (Details) - Options to purchase common stock - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value per stock option (in dollars per share)	$ 0	$ 34.98	$ 34.24
Aggregate intrinsic value on exercise	$ 17	$ 16	$ 60
Cash received upon exercise	66	29	77
Tax benefits realized related to exercise	4	4	22
Total fair value of stock options vested	16	16	20
Total compensation cost, net of estimated forfeitures, related to unvested stock options not yet recognized, pre-tax	$ 6	$ 15	$ 15
Weighted-average period in years over which stock option compensation cost is expected to be recognized	2 years	2 years	2 years

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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