Condensed Consolidated Balance Sheets Parenthetical - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts receivable allowance for doubtful accounts	$ 19,370	$ 20,205
Common Class A [Member]
Common Stock, Shares, Issued	25,044,738	24,966,035
Common Stock, Shares, Outstanding	24,739,501	24,835,804
Common Class B [Member]
Common Stock, Shares, Issued	5,091,003	5,089,532
Common Stock, Shares, Outstanding	5,091,003	5,089,532
Treasury Class A [Member]
Treasury Stock, Shares	305,237	130,231