Long-term Debt (Principal and Issuance Costs and Discounts) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Principal amount of Convertible Notes	$ 3,548	$ 2,300
Issuance costs and discounts	(248)	(11)
Total debt	$ 3,300	$ 2,289
Debt Instrument, Interest Rate, Effective Percentage	4.30%
Senior notes \| 0.25% convertible senior notes due 2025
Debt Instrument [Line Items]
Principal amount of Convertible Notes	$ 1,323
Issuance costs and discounts	(17)
Total debt	$ 1,100

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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