Income Taxes - Change in Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Balance at beginning of the year	$ 7	$ 6	$ 6
Increases related to positions taken during the current year	12	1	0
Balance at end of year	$ 19	$ 7	$ 6