Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance of unrecognized tax benefits	$ 1,248	$ 1,132	$ 1,019
Gross increases based on tax positions related to current year	633	116	113
Gross increases based on tax positions related to prior year	149	0	0
Settlements with taxing authorities	0	0	0
Expiration of statue of limitations	0	0	0
Ending balance of unrecognized tax benefits	$ 2,030	$ 1,248	$ 1,132