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Borrowings - 2018 Term Loan (Details) - USD ($)		6 Months Ended
Borrowings - 2018 Term Loan (Details) - USD ($)	Sep. 28, 2018	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	May 23, 2019
Debt Instrument [Line Items]
Non-current restricted cash		$ 3,467,000	$ 3,867,000	$ 17,968,000
2019 Term Loan, due May 2020 (2) \| Term loan
Debt Instrument [Line Items]
Principal amount	$ 60,000,000.0				$ 60,000,000.0
Term loan \| 2018 Term Loan
Debt Instrument [Line Items]
Debt term (in years)	3 years
Non-current restricted cash		3,500,000
Minimum aggregate principal payment		5,000,000
Borrowings principal repayment (Note 9)		1,000,000
Fair value of term loan		$ 56,200,000