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, 2019	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value per stock option (in dollars per share)	$ 34.98	$ 34.24	$ 32.19
Aggregate intrinsic value on exercise	$ 16	$ 60	$ 97
Cash received upon exercise	29	77	54
Tax benefits realized related to exercise	4	22	38
Total fair value of stock options vested	16	20	18
Total compensation cost, net of estimated forfeitures, related to unvested stock options not yet recognized, pre-tax	$ 15	$ 15	$ 21
Weighted-average period in years over which stock option compensation cost is expected to be recognized	2 years	2 years	2 years

Unrecognized cost of unvested share-based compensation awards.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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Amount of cash inflow from exercise of stock options granted under share-based compensation 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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