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Marketable Securities - Schedule of Marketable Securities (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items] |  |  |
Market value, available for sale securities, current | $ 2.1 |  | $ 4.4
Market value, available for sale securities, noncurrent | 6.2 |  | 2.9
Non Current Assets |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |
Market value, available for sale securities, noncurrent | 6.2 |  | 2.9
Cost basis | 6.2 |  | 2.9
Unrealized gains (losses), net | 0.0 | $ 0.0 |
Current Assets |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |
Cost basis | 2.1 |  | $ 4.4
Unrealized gains (losses), net | $ 0.0 | $ 0.0 |

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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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- Definition Amount of investment in marketable security, classified as noncurrent. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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