Debt - Summary of Long-term Debt (Details) $ in Millions	Mar. 31, 2020 USD ($)	Mar. 31, 2020 EUR (€)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 EUR (€)
Debt Instrument [Line Items]
Principal amount at par	$ 14,780		$ 14,873
Senior Notes
Debt Instrument [Line Items]
Principal amount at par | €		€ 4,700,000,000
Senior Notes | 5.375% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	500		500
Fair value	$ 507		$ 518
Interest rate	5.375%	5.375%	5.375%	5.375%
Senior Notes | 5.500% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 700		$ 700
Fair value	$ 722		$ 744
Interest rate	5.50%	5.50%	5.50%	5.50%
Senior Notes | 5.750% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 400		$ 400
Fair value	$ 426		$ 444
Interest rate	5.75%	5.75%	5.75%	5.75%
Senior Notes | 5.875% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 800		$ 800
Fair value	$ 847		$ 896
Interest rate	5.875%	5.875%	5.875%	5.875%
Senior Notes | 4.375% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 1,000		$ 1,000
Fair value	$ 1,018		$ 1,026
Interest rate	4.375%	4.375%	4.375%	4.375%
Senior Notes | 3.625% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 1,433	€ 1,300,000,000	$ 1,459	€ 1,300,000,000
Fair value	$ 1,433		$ 1,565
Interest rate	3.625%	3.625%	3.625%	3.625%
Senior Notes | 4.875% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 1,600		$ 1,600
Fair value	$ 1,632		$ 1,670
Interest rate	4.875%	4.875%	4.875%	4.875%
Senior Notes | 5.875% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 1,900		$ 1,900
Fair value	$ 2,047		$ 2,111
Interest rate	5.875%	5.875%	5.875%	5.875%
Senior Notes | 4.625% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 1,212	€ 1,100,000,000	$ 1,234	€ 1,100,000,000
Fair value	$ 1,246		$ 1,378
Interest rate	4.625%	4.625%	4.625%	4.625%
Senior Notes | 6.375% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 800		$ 800
Fair value	$ 883		$ 916
Interest rate	6.375%	6.375%	6.375%	6.375%
Senior Notes | 3.875% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 1,323	€ 1,200,000,000	$ 1,346	€ 1,200,000,000
Fair value	$ 1,303		$ 1,429
Interest rate	3.875%	3.875%	3.875%	3.875%
Senior Notes | 5.375% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 900		$ 900
Fair value	$ 942		$ 960
Interest rate	5.375%	5.375%	5.375%	5.375%
Senior Notes | 3.625% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 1,212	€ 1,100,000,000	$ 1,234	€ 1,100,000,000
Fair value	$ 1,191		$ 1,273
Interest rate	3.625%	3.625%	3.625%	3.625%
Senior Notes | 4.875% Senior Notes
Debt Instrument [Line Items]
Principal amount at par	$ 1,000		$ 1,000
Fair value	$ 1,024		$ 1,019
Interest rate	4.875%	4.875%	4.875%	4.875%