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Reconciliation of Our Investment in Restricted Equity Securities Measured at Fair Value on Quarterly Basis Using Significant Unobservable Inputs (Level 3) (Detail) - USD ($) $ in Thousands | 3 Months Ended |  |
--- | --- | --- | ---
Jun. 30, 2019 | Mar. 31, 2019 | Jan. 31, 2019 | Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Investment in restricted equity securities | $ 77,365 |  |  |
Balance at end of period | 77,365 |  |  |
Restricted equity securities |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Investment in restricted equity securities | 77,365 |  |  | $ 0
Balance at end of period | 77,365 |  |  | $ 0
Restricted equity securities | Fair Value Measurements Recurring | Significant Unobservable Inputs (Level 3) | Long-term investments |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Investment in restricted equity securities | 77,365 | $ 56,400 | $ 54,720 |
Net unrealized gain recognized on restricted equity securities during the period | 20,965 | 1,680 |  |
Balance at end of period | $ 77,365 | $ 56,400 | $ 54,720 |

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- Definition Amount of restricted investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 + Details
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