Consolidated Statements of Other Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 837	$ 3,039	$ 1,019
Other comprehensive income (loss), net of tax:
Net gains (losses) on available-for-sale securities	4	(3)	7
Net gains (losses) on derivative instruments	(68)	17	88
Foreign currency translation adjustments	64	(34)	(21)
Total other comprehensive income (loss), net of tax	0	(20)	74
Total comprehensive income (loss)	$ 837	$ 3,019	$ 1,093