Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrecognized Tax Benefits [Roll Forward]
Beginning of year balance	$ 185	$ 43	$ 613
Additions based on prior year tax positions	2	130	2
Additions based on current year tax positions	11	12	21
Reduction for prior year tax positions	(5)	0	(48)
Reductions for settlements	0	0	(545)
End of year balance	$ 193	$ 185	$ 43