Stock Incentive Plans - Schedule of Stock-Based Compensation (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement [Abstract]
Total share-based compensation cost	$ 30	$ 19	$ 48	$ 41
Related income tax benefit	7	3	11	6
Total intrinsic value of options exercised	1	25	7	35
Tax benefits from exercised stock options and awards	$ 1	$ 14	$ 10	$ 19

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of tax benefit 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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