Stockholders' Equity - Share Repurchases (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased (in shares)	15,933,651	19,342,586	1,537,782
Average price per share (in dollars per share)	$ 46.21	$ 69.20	$ 89.41
Share repurchase amount	$ 736	$ 1,339	$ 137
Open Market Purchases
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased (in shares)	12,279,107	19,342,586	1,537,782
Average price per share (in dollars per share)	$ 43.67	$ 69.20	$ 89.41
Share repurchase amount	$ 536	$ 1,339	$ 137
Accelerated Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased (in shares)	3,654,544
Average price per share (in dollars per share)	$ 54.73
Share repurchase amount	$ 200

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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