Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Tax Credit Carryforward [Line Items]
Reversal of tax reserve		$ 903
Tax Reserve Member
Tax Credit Carryforward [Line Items]
Reversal of tax reserve		600
Unrecognized Tax Benefits Reserve Accrued Interest Member
Tax Credit Carryforward [Line Items]
Reversal of tax reserve		$ 300
Forecast
Tax Credit Carryforward [Line Items]
Reversal of tax reserve	$ 500