Fair Value Measurements - Narrative (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020	May 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Restricted cash	$ 6,660,000	$ 6,660,000
Amortized cost of available-for-sale investments with maturities less than one year	784,300,000	866,500,000
Amortized cost of available-for-sale investments with maturities greater than one year	63,300,000	56,500,000
Net unrealized gains on investments, net of tax	0	200,000
Convertible senior notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate			0.75%
Debt instrument, fair value	1,154,300,000
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized gain	0	0
Unrealized loss	$ 0	$ 0

Cash And Cash Equivalents, Accumulated Gross Unrealized Gain, Before Tax

No definition available.

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- Definition

Cash And Cash Equivalents, Accumulated Gross Unrealized Loss, Before Tax

+ References

No definition available.

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- Definition

Debt Securities, Available-For-Sale, Maturity, Allocated And Single Maturity Date, After One Year, Amortized Cost

+ References

No definition available.

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- Definition

Amount, after tax, of accumulated unrealized gain (loss) on 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/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
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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), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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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.

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- Definition

Amount of cash restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 4
-Subparagraph (a)
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-Name Accounting Standards Codification
-Topic 230
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