Debt - Components of Debt Obligations and Weighted Average Interest Rate (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt, gross	$ 30,620	$ 33,694
Finance lease liability	141	189
Total long-term debt	30,761	33,883
Unaccreted discount and issuance costs	(240)	(324)
Current portion of long-term debt	3,033	3,232
Long-term debt, net of current portion	27,488	30,327
Total long-term debt, net of unaccreted discount and issuance costs	30,521	33,559
Line of credit | Borrowing under Wells Fargo Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 20,341	$ 21,030
Weighted average interest rate	1.93%	2.01%
Notes payable to banks | Mitsubishi Bank loans
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,167	$ 7,662
Notes payable to banks | Mitsubishi Bank loans | Minimum
Debt Instrument [Line Items]
Weighted average interest rate	1.07%	1.05%
Notes payable to banks | Mitsubishi Bank loans | Maximum
Debt Instrument [Line Items]
Weighted average interest rate	1.47%	1.45%
Notes payable to banks | Mitsubishi Bank and Yamanashi Chuo Bank loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 4,112	$ 5,002
Weighted average interest rate	1.07%	1.07%