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Fair Value Measurements - Schedule of Financial Instruments and the Related Fair Value Hierarchy of the Valuation Techniques Utilized (Detail) - Fair Value, Nonrecurring [Member] - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
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Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Assets | $ 311,979 | $ 281,314
Total Financial Liabilities | 370,994 | 149,496
Money Market Funds [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Assets | 271,158 | 281,314
Bank Certificates of Deposit [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Assets | 40,821 |
Convertible Senior Notes [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Liabilities | 370,994 | 149,496
Level 1 [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Assets | 311,979 | 281,314
Level 1 [Member] | Money Market Funds [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Assets | 271,158 | 281,314
Level 1 [Member] | Bank Certificates of Deposit [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Assets | 40,821 |
Level 3 [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Liabilities | 370,994 | 149,496
Level 3 [Member] | Convertible Senior Notes [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Total Financial Liabilities | $ 370,994 | $ 149,496

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities. + References No definition available. + Details
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