Debt - Maturities (Details) $ in Millions	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Net carrying amount	$ 1,262
2020	18
2021	16
2022	722
2023	22
2024	154
Thereafter	$ 330
5.375% Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate	5.375%
4.875% Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate	4.875%
1.125% Convertible Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate	1.125%
Senior Notes \| 5.375% Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate	5.375%
Net carrying amount	$ 700
2020	0
2021	0
2022	700
2023	0
2024	0
Thereafter	$ 0
Senior Notes \| 4.875% Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate	4.875%
Net carrying amount	$ 330
2020	0
2021	0
2022	0
2023	0
2024	0
Thereafter	$ 330
Senior Notes \| 1.125% Convertible Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate	1.125%
Term Loan Facility \| Term Loan Facility
Debt Instrument [Line Items]
Net carrying amount	$ 220
2020	6
2021	16
2022	22
2023	22
2024	154
Thereafter	$ 0
Convertible Debt \| 4.875% Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate	4.875%
Convertible Debt \| 1.125% Convertible Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate	1.125%
Net carrying amount	$ 12
2020	12
2021	0
2022	0
2023	0
2024	0
Thereafter	$ 0

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 470
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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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