Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts and notes receivable, allowance	$ 9,774	$ 7,980
Property and equipment, accumulated depreciation	$ 14,117	$ 13,280
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	17,809,119	17,754,416
Common stock, shares outstanding	17,809,119	17,754,416
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