Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts and notes receivable, allowance	$ 11,724	$ 12,538
Property and equipment, accumulated depreciation	$ 14,731	$ 14,940
Common Class A
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	180,000,000	180,000,000
Common stock, shares issued	18,390,691	17,838,233
Common stock, shares outstanding	18,390,691	17,838,233
Common Class B
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	1,000	1,000
Common stock, shares issued	1	1
Common stock, shares outstanding	1	1