Stockholders' Equity, Convertible Preferred Stock and Redeemable Non-controlling Interest (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance			$ 7,485
Loss attributable to non-controlling interest	$ 203	$ 28	367	$ 300
Ending balance	7,716		7,716
Qingdao Xingyang City Investment
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance			7,485	0
Initial investment			0	7,047
Accretion of dividend			231	213
Loss attributable to non-controlling interest			(175)	(80)
Adjustment to redemption value			175	80
Ending balance	$ 7,716	$ 7,260	$ 7,716	$ 7,260