Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017
Components of accrued liabilities [Abstract]
Preferred stock dividends payable	$ 2,901		$ 2,901
Accrued compensation and related charges	2,580		3,205
Payable in connection with purchase of subsidiary shares from noncontrolling interests	1,192
Advance from customers	927	$ 1,061	924
Dividends payable by consolidated joint ventures	524		533	$ 512
Accrued professional services	409		570
Accrued income taxes	341		270
Current portion of royalty payments	288		575
Other personnel related costs	221		230
Accrued product warranty	178		133
Other tax payable	85		395
Accrual for sales refund liabilities	82
Other accrued liabilities	2,065		1,413
Accrued liabilities, total	$ 11,793		$ 11,149