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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

X

- 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 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/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117546-209714

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