Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 247	$ 119	$ 715	$ 289
Other comprehensive income, net of tax
Net unrealized losses on available-for-sale debt securities [net of tax benefit of $6, $7, $8 and $14, respectively]	(21)	(25)	(29)	(51)
Reclassification of net (gains) losses realized on available-for sale debt securities included in investment and other income, net [net of tax provision of $0, $0, $0 and $0, respectively]	(1)	2	(1)	2
Other comprehensive loss	(22)	(23)	(30)	(49)
Comprehensive income	$ 225	$ 96	$ 685	$ 240