Stockholders' Equity - Schedule of Other Comprehensive Income (Loss), Net of Tax (Details) € in Millions, £ in Millions, $ in Millions	3 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 EUR (€)	Jun. 30, 2020 GBP (£)	Mar. 31, 2020 EUR (€)	Sep. 30, 2019 GBP (£)	Jun. 30, 2019 EUR (€)	Jun. 30, 2019 GBP (£)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	$ 27	$ 64
Reclassified to income statement, net of income tax expense	2	13
Other comprehensive income, net of tax	29	77
Foreign currency translation adjustments arising during period, tax	0	0
Reclassified to income statement, tax	0	0
Unrealized gains on cash flow hedges arising during period, tax	0	6
Net actuarial loss and prior service cost arising during the period, tax	0	(1)
Amortization of actuarial (gain) loss and prior service costs, tax	0	0
Foreign currency translation adjustments and other, tax	0	0
Net actuarial gain (losses) attributable to redeemable noncontrolling interest	3	0
Foreign Currency Translation Adjustments, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	96	70
Reclassified to income statement, net of income tax expense	0	0
Other comprehensive income, net of tax	96	70
Translation gain (loss) attributable to redeemable noncontrolling interest	58	6
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(63)	(26)
Reclassified to income statement, net of income tax expense	0	0
Other comprehensive income, net of tax	(63)	(26)
Unrealized gains (losses) on net investment hedges arising during period, tax	22	9
Reclassified to income statement, tax	0	0
Unrealized gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(5)	12
Reclassified to income statement, net of income tax expense	0	0
Other comprehensive income, net of tax	(5)	12
Reclassified to income statement, tax	0	0
Net actuarial gain and prior service cost arising during the period, net of income tax expense of nil and $1
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	0	6
Amortization of actuarial loss, prior service cost and transition obligation, net of income tax expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	2	1
Foreign currency translation adjustments and other, net of income tax expense of nil and nil
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(1)	2
Changes in retirement-related benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassified to income statement, net of income tax expense	0	12
Other comprehensive income, net of tax	1	21
Reclassified to income statement, tax	0	5
Euro Denominated Notes | Term Loan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Long-term debt outstanding | €							€ 1,950
British Pound Sterling Denominated Notes | Term Loan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Long-term debt outstanding | £				£ 450		£ 450		£ 450
Net Investment Hedging | Euro Denominated Notes | Term Loan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Long-term debt outstanding | €			€ 1,700		€ 1,700
Derivatives designated for hedge accounting
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain (loss) from net investment hedges recorded within other comprehensive income	(34)	(24)
Derivatives designated for hedge accounting | Net Investment Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivatives used in net investment hedge, gains (loss) gross	$ (51)	$ (11)