Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 2,017	$ 913	$ 795
Other comprehensive income, net of tax
Net unrealized gains on available-for-sale marketable securities [net of tax provision of ($2), ($4) and ($5), respectively]	9	13	11
Reclassification adjustment for net (gains) losses on available-for-sale marketable securities included in investment and other income, net [net of tax provision (benefit) of $5, $0 and ($3), respectively]	(16)	(1)	9
Other comprehensive (loss) income	(7)	12	20
Comprehensive income	$ 2,010	$ 925	$ 815