Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Balance	$ 5,129	$ 11,725
Current-period other comprehensive income (loss)	9	(104)
Amounts reclassified from accumulated other comprehensive loss	(5)	(3)
Balance	4,942	11,217
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Balance	(851)	(517)
Current-period other comprehensive income (loss)	(2)	(111)
Amounts reclassified from accumulated other comprehensive loss	0
Balance	(853)	(628)
Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Balance	(20)	(3)
Current-period other comprehensive income (loss)	7	6
Amounts reclassified from accumulated other comprehensive loss	4	(2)
Balance	(9)	1
Available-for-sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Balance	9	9
Current-period other comprehensive income (loss)	4	1
Amounts reclassified from accumulated other comprehensive loss	0
Balance	13	10
Pension and Other Post-retirement Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Balance	259	267
Current-period other comprehensive income (loss)	0
Amounts reclassified from accumulated other comprehensive loss	(9)	(1)
Balance	250	266
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Balance	(603)	(244)
Balance	$ (599)	$ (351)