CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Preferred stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	3,707,256	3,707,256
Preferred stock, shares outstanding (in shares)	3,567,543	3,567,543
Treasury stock, at cost (in shares)	144,594	144,594
Trade Accounts Receivable
Allowance for doubtful accounts	$ 2,698	$ 3,942
Common Class A
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	120,000,000	120,000,000
Common stock, shares issued (in shares)	14,771,878	14,771,878
Common stock, shares outstanding (in shares)	14,627,284	14,627,284
Common Class B
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	20,800,000	20,800,000
Common stock, shares outstanding (in shares)	20,800,000	20,800,000