Income Taxes - Operating Loss and Tax Credit Carryforwards (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 132	$ 15
Net operating loss carryforward with no expiration	128	3
Net operating loss carryforward with expiration	4	12
Tax credit carryforwards	5	9
Tax credit carryforwards with no expiration	0	0
Tax credit carryforwards with expiration	5	9
Capital loss carryforwards	0	0
Capital loss carryforwards with no expiration	0	0
Capital loss carryforwards with expiration	0	0
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	369	673
Net operating loss carryforward with no expiration	6	6
Net operating loss carryforward with expiration	363	667
Tax credit carryforwards	0	16
Tax credit carryforwards with no expiration	0	7
Tax credit carryforwards with expiration	0	9
Capital loss carryforwards	0	0
Capital loss carryforwards with no expiration	0	0
Capital loss carryforwards with expiration	0	0
Foreign
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	16,700	10,512
Net operating loss carryforward with no expiration	6,191	6,471
Net operating loss carryforward with expiration	10,509	4,041
Tax credit carryforwards	0	16
Tax credit carryforwards with no expiration	0	0
Tax credit carryforwards with expiration	0	16
Capital loss carryforwards	45	59
Capital loss carryforwards with no expiration	45	40
Capital loss carryforwards with expiration	$ 0	$ 19