Consolidated Statements of Shareholder's Equity - USD ($) $ in Millions	Total	Cumulative Effect Period of Adoption Adjustment	Capital stock	Additional paid-in capital	Accumulated other comprehensive (loss) income	Accumulated other comprehensive (loss) income Cumulative Effect Period of Adoption Adjustment	Retained earnings	Retained earnings Cumulative Effect Period of Adoption Adjustment
Balance at Mar. 31, 2018	$ 12,880		$ 915	$ 2	$ (29)		$ 11,992
Balance (ASU 2014-09) at Mar. 31, 2018		$ (110)				$ 12		$ (122)
Net income	795		0	0	0		795
Other comprehensive income (loss), net of tax	20		0	0	20		0
Dividends, net of tax	(7)		0	0	0		(7)
Balance at Mar. 31, 2019	13,578		915	2	3		12,658
Net income	913		0	0	0		913
Other comprehensive income (loss), net of tax	12		0	0	12		0
Balance at Mar. 31, 2020	14,503		915	2	15		13,571
Balance (ASU 2016-13) at Mar. 31, 2020		$ (218)						$ (218)
Net income	2,017		0	0	0		2,017
Other comprehensive income (loss), net of tax	(7)		0	0	(7)		0
Dividends, net of tax	(700)		0	0	0		(700)
Balance at Mar. 31, 2021	$ 15,595		$ 915	$ 2	$ 8		$ 14,670