Summary of Significant Accounting Policies - Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Provision for slow-moving and obsolete inventories	$ (600)	$ (600)
Reduction of gross inventory levels	$ (1,200)	$ 1,900