Stockholders' Equity (Deficit) - Schedule of Other Comprehensive Income (Loss), Net of Tax (Details) € in Millions, £ in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 EUR (€)	Dec. 31, 2020 GBP (£)	Mar. 31, 2020 EUR (€)	Dec. 31, 2019 EUR (€)	Dec. 31, 2019 GBP (£)	Sep. 30, 2019 GBP (£)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	$ 50	$ 45	$ 90	$ 86
Reclassified to income statement, net of income tax expense	69	6	71	98
Other comprehensive income (loss)	119	51	161	184
Foreign currency translation adjustments, tax	0	0	0	0
Reclassified to income statement, tax	0	0	0	0
Unrealized gains (loss) on cash flow hedges arising during period, tax	2	3	6	(7)
Net actuarial loss and prior service cost arising during the period, tax	0	0	0	1
Amortization of actuarial (gain) loss and prior service costs, tax	2	0	1	0
Foreign currency translation adjustments and other, tax	0	0	0	0
Net actuarial gain (losses) attributable to redeemable noncontrolling interest	5	(2)	3	(1)
Foreign Currency Translation Adjustments, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	156	101	363	57
Reclassified to income statement, net of income tax expense	47	0	47	0
Other comprehensive income (loss)	203	101	410	57
Translation gain (loss) attributable to redeemable noncontrolling interest	20	12	(41)	(1)
Unrealized Gains (Losses) on Net Investment Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(96)	(58)	(229)	(2)
Reclassified to income statement, net of income tax expense	0	0	0	0
Other comprehensive income (loss)	(96)	(58)	(229)	(2)
Unrealized gains (losses) on net investment hedges arising during period, tax	33	21	80	1
Reclassified to income statement, tax	0	0	0	0
Gain (loss) from net investment hedges recorded within other comprehensive income	0		(1)
Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	(12)	8	(36)	33
Reclassified to income statement, net of income tax expense	0	0	0	0
Other comprehensive income (loss)	(12)	8	(36)	33
Reclassified to income statement, tax	0	0	0	0
Net actuarial loss and prior servicecost arising during the period, net of income tax benefit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	0	0	0	(3)
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)	(2)	0	0
Foreign currency translation adjustments and other, net of income tax expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications	2	(6)	(8)	1
Changes in retirement-related benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassified to income statement, net of income tax expense	24	8	24	98
Other comprehensive income (loss)	24	0	16	96
Reclassified to income statement, tax	9	3	9	35
Euro Denominated Notes | Term Loan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Long-term debt outstanding | €								€ 1,700
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	(84)	(59)	(201)	8
Derivatives designated for hedge accounting | Net Investment Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivatives used in net investment hedge, gains (losses) gross	$ (45)	$ (20)	$ (108)	$ (11)