Income Taxes - Reconciliation of the Beginning and Ending Amount of Unrecognized Income Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized income tax benefits	$ 894	$ 944
Increases for tax positions related to prior years	0	9	$ 422
Increases for tax positions related to current year	479	394	522
Decreases for tax positions related to prior years	(101)	(453)	0
Decreases for tax positions related to current year	0	0	0
Settlement with taxing authorities	0	0	0
Expiration of applicable statutes of limitations	0	0	0
Unrecognized income tax benefits	$ 1,272	$ 894	$ 944