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Cash and Cash Equivalents and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Sep. 25, 2020	Jun. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 614,236	$ 485,928		$ 133,583
Cash equivalents	566,900	447,200
Convertible Senior Notes \| Convertible Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long-term debt	931,200
Carrying value of debt	$ 477,554	$ 467,201	$ 461,800