Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 1,712	$ 1,460	$ 979
Other comprehensive income, net of tax
Net unrealized gains (losses) on available-for-sale debt securities [net of tax (provision) benefit of ($2), $2 and $10, respectively]	7	(7)	(37)
Reclassification of net losses (gains) realized on available-for-sale debt securities included in investment and other income, net [net of tax benefit of $1, $0 and $0, respectively]	2	(1)	1
Other comprehensive income (loss)	9	(8)	(36)
Comprehensive income	$ 1,721	$ 1,452	$ 943