Cash and Cash Equivalents - Cash and Cash Equivalents by Geographic Region (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 74,302	$ 53,207
United States
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	16,751	1,156
People's Republic of China (PRC)
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	13,700	20,885
Asia (excluding the PRC)
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	21,691	2,398
Europe
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	9,081	19,907
South America
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 13,079	$ 8,861