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Short-Term Deposits and Marketable Securities - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Financing Receivable Recorded Investment [Line Items] |  |  |
Short-term deposits | $ 581,000,000 | $ 4,000,000 |
Marketable securities | 133,000,000 | 133,000,000 | $ 330,000,000
Proceeds from matured marketable securities |  | 200,000,000 | 100,000,000
Investment of available cash in short-term deposits | 581,000,000 |  |
Debt securities, allowance recognized | 0 |  |
U.S. Treasury Debt Securities [Member] |  |  |
Financing Receivable Recorded Investment [Line Items] |  |  |
Marketable securities | $ 133,000,000 | 133,000,000 | $ 330,000,000
Proceeds from matured marketable securities |  | $ 200,000,000 |
Weighted average maturity period | 6 months |  |
Aggregate amortized cost basis of securities | $ 132,000,000 |  |

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- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 + Details
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