Cash Equivalents and Investments - Narrative (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($) Investment	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) Investment	Jun. 30, 2019 USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Total investments in unrealized loss position \| Investment	121		121
Available-for-sale debt securities, gross realized gain	$ 0	$ 0	$ 0	$ 0
Available-for-sale debt securities, gross realized loss	0	0	0	0
Equity investments, unrealized gains	0	0	0	0
Equity investments, unrealized losses	0	0	0	0
Restricted cash and investments	90,100,000		90,100,000
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	68,000,000.0		68,000,000.0
Other long-term assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	22,100,000		22,100,000
Debt Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Allowance for credit losses	0	0	0	0
Allowance for credit losses	$ 0	$ 0	$ 0	$ 0

Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of increase (decrease) in allowance for credit loss of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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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).

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Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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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.

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Cash and investments whose use in whole or in part is restricted for the long-term, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

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