Income Taxes - Change in Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Balance at beginning of the year	$ 19	$ 7	$ 6
Increases related to positions taken during the current year	1	12	1
Increases recorded in current year related to positions taken during prior years	2	0	0
Expirations due to lapse of statute	(7)	0	0
Balance at end of year	$ 15	$ 19	$ 7