Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 1,421	$ 293
Other comprehensive income (loss), net of tax:
Net gains (losses) on available-for-sale securities	3	0
Net gains (losses) on derivative instruments	9	93
Foreign currency translation adjustments	1	(15)
Total other comprehensive income (loss), net of tax	13	78
Total comprehensive income (loss)	$ 1,434	$ 371