Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 429	$ 178	$ 786	$ 570
Other comprehensive income, net of tax
Net unrealized gains (losses) on available-for-sale debt securities [net of tax (provision) benefit of ($6), $6, ($5) and $8, respectively]	21	(21)	16	(29)
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]	0	(1)	3	(1)
Other comprehensive income (loss)	21	(22)	19	(30)
Comprehensive income	$ 450	$ 156	$ 805	$ 540