Income Taxes - Income Tax Related Assets And Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Current assets:
Income tax receivables and prepaid taxes	$ 113	$ 154
Non-current:
Income taxes receivable and prepaid taxes	137	30
Deferred tax assets	355	373
Deferred tax assets, noncurrent	492	403
Deferred tax assets, total	605	557
Current liabilities:
Liability for Uncertainty in Income Taxes, Current	0	(15)
Income taxes payable	(208)	(112)
Deferred tax liabilities, current	(208)	(127)
Non-current:
Deferred taxes	(767)	(652)
Income taxes payable	(201)	(278)
Liability for uncertain tax positions	(216)	(236)
Deferred tax liabilities, noncurrent	(1,184)	(1,166)
Deferred tax liabilities, total	(1,392)	(1,293)
Valuation allowance	1,575	$ 1,440
Net increase (decrease) in deferred tax asset valuation allowance	$ 135