Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) - Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning balance	$ 5,129	$ 11,725	$ 13,837
Current-period other comprehensive income (loss)	302	(349)	(299)
Amounts reclassified from accumulated other comprehensive income (loss), net of taxes	(1)	(10)	(3)
Ending balance	5,308	5,129	11,725
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning balance	(851)	(517)	(261)
Current-period other comprehensive income (loss)	297	(334)	(256)
Amounts reclassified from accumulated other comprehensive income (loss), net of taxes	0	0	0
Ending balance	(554)	(851)	(517)
Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning balance	(20)	(3)	9
Current-period other comprehensive income (loss)	14	(15)	(22)
Amounts reclassified from accumulated other comprehensive income (loss), net of taxes	5	(2)	10
Ending balance	(1)	(20)	(3)
Available-for-sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning balance	9	9	9
Current-period other comprehensive income (loss)	(9)	0	0
Amounts reclassified from accumulated other comprehensive income (loss), net of taxes	0	0	0
Ending balance	0	9	9
Pension and Other Post-retirement Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning balance	259	267	301
Current-period other comprehensive income (loss)	0	0	(21)
Amounts reclassified from accumulated other comprehensive income (loss), net of taxes	(6)	(8)	(13)
Ending balance	253	259	267
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning balance	(603)	(244)	58
Ending balance	$ (302)	$ (603)	$ (244)