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, 2020	$ 14,503		$ 915	$ 2	$ 15	$ 13,571
Balance (ASU 2016-13) at Mar. 31, 2020		$ (218)					$ (218)
Net income	1,697		0	0	0	1,697
Other comprehensive income (loss), net of tax	11		0	0	11	0
Balance at Dec. 31, 2020	15,993		915	2	26	15,050
Balance at Sep. 30, 2020	15,325		915	2	26	14,382
Net income	668		0	0	0	668
Other comprehensive income (loss), net of tax	0		0	0	0	0
Balance at Dec. 31, 2020	15,993		915	2	26	15,050
Balance at Mar. 31, 2021	15,595		915	2	8	14,670
Net income	2,291		0	0	0	2,291
Other comprehensive income (loss), net of tax	3		0	0	3	0
Balance at Dec. 31, 2021	17,889		915	2	11	16,961
Balance at Sep. 30, 2021	17,145		915	2	15	16,213
Net income	748		0	0	0	748
Other comprehensive income (loss), net of tax	(4)		0	0	(4)	0
Balance at Dec. 31, 2021	$ 17,889		$ 915	$ 2	$ 11	$ 16,961