Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 622	$ 655	$ 1,543	$ 1,029
Other comprehensive income, net of tax
Net unrealized (losses) gains on available-for-sale marketable securities [net of tax (benefit) provision of ($1), $1, $2 and $6, respectively]	(2)	1	7	24
Reclassification adjustment for net gains on available-for-sale marketable securities included in investment and other income, net [net of tax provision of $0, $1, $0 and $4, respectively]	0	(2)	0	(13)
Other comprehensive (loss) income	(2)	(1)	7	11
Comprehensive income	$ 620	$ 654	$ 1,550	$ 1,040