Stockholders' Equity - Schedule of Other Comprehensive Income (Loss), Net of Tax (Details) € in Millions, £ in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 EUR (€)	Dec. 31, 2019 GBP (£)	Sep. 30, 2019 GBP (£)	Mar. 31, 2019 USD ($)	Mar. 31, 2019 EUR (€)	Mar. 31, 2019 GBP (£)	Dec. 31, 2018 EUR (€)	Dec. 31, 2018 GBP (£)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	$ 45	$ (76)	$ 86	$ (169)
Reclassified to income statement, net of income tax expense	6	1	98	5
Other Comprehensive Income (Loss), Net of Tax	51	(75)	184	(164)
Foreign currency translation adjustments arising during period, tax	0	0	0	0
Reclassified to income statement, tax	0	0	0	0
Unrealized gains on cash flow hedges arising during period, tax	3	(5)	(7)	(5)
Net actuarial loss and prior service cost arising during the period, tax	0	0	1	0
Amortization of actuarial (gain) loss and prior service costs, tax	0	1	0	(1)
Foreign currency translation adjustments and other, tax	0	0	0	0
Long-term debt outstanding	7,700		7,700					$ 7,600
Net actuarial gain (losses) attributable to redeemable noncontrolling interest	(2)	0	(1)	2
Foreign Currency Translation Adjustments, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	101	(188)	57	(456)
Reclassified to income statement, net of income tax expense	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax	101	(188)	57	(456)
Translation gain (loss) attributable to redeemable noncontrolling interest	12	(11)	(1)	(57)
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(58)	75	(2)	240
Reclassified to income statement, net of income tax expense	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax	(58)	75	(2)	240
Unrealized gains (losses) on net investment hedges arising during period, tax	21	(27)	1	(85)
Reclassified to income statement, tax	0	0	0	0
Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	8	35	33	37
Reclassified to income statement, net of income tax expense	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax	8	35	33	37
Reclassified to income statement, tax	0	0	0	0
Accumulated Defined Benefit Plans Adjustment, Net Prior Service and Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	0	0	(3)	0
Accumulated Defined Benefit Plans Adjustment, Amortization of Actuarial Loss, Prior Service Cost and Transition Obligation, Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(2)	1	0	5
Accumulated Defined Benefit Plans, Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(6)	2	1	10
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassified to income statement, net of income tax expense	8	0	98	0
Other Comprehensive Income (Loss), Net of Tax	0	3	96	15
Reclassified to income statement, tax	3	0	35	0
Euro Denominated Notes | Term Loan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Long-term debt outstanding | €					€ 250						€ 1,950
British Pound Sterling Denominated Notes | Term Loan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Long-term debt outstanding | £						£ 450	£ 450			£ 450		£ 450
Net Investment Hedging | Euro Denominated Notes | Term Loan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Long-term debt outstanding | €					€ 1,700				€ 1,950
Derivatives designated for hedge accounting
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain (loss) from net investment hedges recorded within other comprehensive income	(59)	39	(8)	223
Derivatives designated for hedge accounting | Net Investment Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivatives used in net investment hedge, gains (loss) gross	$ (20)	$ 63	$ (11)	$ 102