Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2024	Dec. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 429	$ 561	$ 1,215	$ 1,131
Other comprehensive income, net of tax
Net unrealized gains (losses) on available-for-sale debt securities [net of tax (provision) benefit of $6, $(8), $1 and $0, respectively]	(21)	30	(4)	1
Reclassification of net losses (gains) realized on available-for-sale debt securities included in investment and other income, net [net of tax (benefit) provision of $0, $0, ($1) and $0, respectively]	0	0	2	(1)
Other comprehensive income (loss)	(21)	30	(2)	0
Comprehensive income	$ 408	$ 591	$ 1,213	$ 1,131