Other Current Liabilities - Schedule of Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities, Current [Abstract]
Accrued legal	$ 2,202	$ 3,096
Income taxes payable	219	164
Other current liabilities	1,475	1,149
Total other current liabilities	$ 3,896	$ 4,409