Income Taxes - Additional information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Statutory income tax rates		34.00%
Statutory income tax rates		35.00%
Cumulative loss, period		3 years
Valuation allowance		$ 16,590,000	$ 18,882,000
Net operating loss carryforwards , expiration date		Dec. 31, 2036
Ownership change percent of equity ownership		50.00%
Period for ownership change		3 years
Uncertain tax positions		$ 76,000	83,000	$ 50,000
Accrued interest and penalties related to uncertain tax positions		11,000	8,000
Net deferred tax assets, before valuation allowance		7,200,000
Unremitted earnings		200,000
Scenario, Plan
Income Tax Disclosure [Line Items]
Statutory income tax rates	21.00%
Federal
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		52,400,000	46,200,000
State
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		$ 45,600,000	$ 40,500,000
China
Income Tax Disclosure [Line Items]
Statutory income tax rates		25.00%
U.K.
Income Tax Disclosure [Line Items]
Statutory income tax rates		20.00%
SWEDEN
Income Tax Disclosure [Line Items]
Statutory income tax rates		22.00%