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Fair Value Measurements Narrative (Details) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 USD ($) Loans | Dec. 31, 2020 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Agreements Not Publicly Held | Loans | 5 |
1.250 Convertible Senior Notes due 2025 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Instrument, Convertible, Conversion Ratio | 25.9909 |
1.250 Convertible Senior Notes due 2025 | Unsecured Debt |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Stated interest rate | 1.25% |
1.250 Convertible Senior Notes due 2025 | Convertible Debt [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Instrument, Convertible, Carrying Amount of Equity Component | $ | $ 403 | $ 403

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