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Summary of Significant Accounting Policies - Fair Value Measurements and Other Long-Term Investments (Details) | 12 Months Ended
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Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
Variance threshold for outliers | $ 500,000
Variance threshold for outliers, percent | 5.00%
Other long-term investments | $ 856,000,000
Level 3 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
Other long-term investments | 654,000,000
Fair Value Measured at Net Asset Value Per Share |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
Other long-term investments | $ 202,000,000

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