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 income (loss)	Retained earnings	Retained earnings Cumulative Effect Period of Adoption Adjustment
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 [Member]) 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	(700)		0	0	0	(700)
Balance at Mar. 31, 2021	15,595		915	2	8	14,670
Net income	2,535		0	0	0	2,535
Other comprehensive income (loss), net of tax	(29)		0	0	(29)	0
Balance at Mar. 31, 2022	$ 18,101		$ 915	$ 2	$ (21)	$ 17,205