Fair Value Measurements - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) $ / shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	May 01, 2020 USD ($) $ / shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Initial conversion price (in USD per share) | $ / shares	$ 38.48		$ 38.48
Other (gains) losses, net	$ (29,000,000)	$ (35,000,000)	$ 32,000,000	$ (95,000,000)
Capital in excess of par value	4,251,000,000		4,251,000,000		$ 4,191,000,000
Loss on repurchase of debt instrument	(12,000,000)	$ 0	$ (12,000,000)	$ 0
Equity feature of partial extinguishment of convertible notes	$ (42,000,000)
Amortization period (in years)	5 years
1.250 Convertible Senior Notes due 2025 | Convertible Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount						$ 2,300,000,000
Stated interest rate	1.25%		1.25%			1.25%
Initial conversion ratio	0.0259909
Initial conversion price (in USD per share) | $ / shares						$ 38.48
Effective interest rate	5.20%		5.20%
Interest expense	$ 40,000,000		$ 96,000,000
Unamortized debt discount	(289,000,000)		(289,000,000)		$ (355,000,000)
If-converted value in excess of principal amount	748,000,000
1.250 Convertible Senior Notes due 2025 | Convertible Debt | September 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount of debt repurchased	80,000,000		80,000,000
Cash paid for repurchased debt	121,000,000		121,000,000
Loss on repurchase of debt instrument	12,000,000
Unamortized debt discount	(12,000,000)		(12,000,000)
Equity feature of partial extinguishment of convertible notes			42,000,000
1.250 Convertible Senior Notes due 2025 | Convertible Debt | Non-Cash Amortization of Debt Discount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest expense	29,000,000		66,000,000
1.250 Convertible Senior Notes due 2025 | Convertible Debt | Non-Cash Amortization of Debt Issuance Costs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest expense	4,000,000		8,000,000
1.250 Convertible Senior Notes due 2025 | Convertible Debt | Contractual Coupon Interest Expense
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest expense	$ 7,000,000		$ 22,000,000