Stockholders' Equity - Schedule of Share Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Jan. 31, 2021	May 31, 2018
Accelerated Share Repurchases [Line Items]
Additional authorized				$ 2,000	$ 4,000
Approximate Dollar Value of Shares that May Yet Be Purchased Under the Programs
Beginning balance	$ 1,535	$ 3,469	$ 1,096
Ending balance	$ 2,785	$ 1,535	$ 3,469
Open Market Transactions
Accelerated Share Repurchases [Line Items]
Total Number of Shares Purchased (in shares)	4.7	9.2	10.4
Average price paid per share (in dollars per share)	$ 160.33	$ 144.68	$ 132.14
Approximate Dollar Value of Shares that May Yet Be Purchased Under the Programs
Shares repurchased	$ (750)	$ (1,334)	$ (1,377)
Accelerated Share Repurchase
Accelerated Share Repurchases [Line Items]
Total Number of Shares Purchased (in shares)		4.7	2.1
Average price paid per share (in dollars per share)		$ 127.68	$ 117.98
Approximate Dollar Value of Shares that May Yet Be Purchased Under the Programs
Shares repurchased		$ (600)	$ (250)