Balance Sheets Details - Accrued Liabilities (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of accrued liabilities
Accrued compensation and related charges	$ 3,307,000	$ 3,440,000
Preferred stock dividends payable	2,901,000	2,901,000
Payable in connection with construction	1,447,000	2,912,000
Payable in connection with land restoration of Nanjing JinMei factory	703,000
Accrued professional services	630,000	706,000
Advance from customers	396,000	476,000
Accrued product warranty	387,000	236,000	$ 133,000
Current portion of operating lease liabilities	319,000
Other personnel-related costs	180,000	202,000
Accrued income taxes	171,000	99,000
Payable in connection with repurchase of subsidiaries shares	151,000	1,147,000
Other tax payable	50,000	261,000
Accrual for sales returns	26,000	47,000
Deferred government grant income in connection with purchase of land		1,000,000
Dividends payable by consolidated joint ventures	0	504,000	$ 533,000
Other accrued liabilities	1,013,000	1,440,000
Accrued liabilities, Total	$ 11,681,000	$ 15,371,000