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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			9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Jan. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment in restricted equity securities	$ 48,915			$ 48,915
Net unrealized Gain (loss) recognized on restricted equity securities during the period	(28,450)			(5,805)
Balance at end of period	48,915			48,915
Restricted equity securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment in restricted equity securities	48,915			48,915
Balance at end of period	48,915			48,915
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	48,915	$ 77,365	$ 56,400	48,915	$ 54,720
Net unrealized Gain (loss) recognized on restricted equity securities during the period	(28,450)	20,965	1,680
Balance at end of period	$ 48,915	$ 77,365	$ 56,400	$ 48,915	$ 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

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Amount of unrealized gain (loss) on 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/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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