Condensed Consolidated Balance Sheets Parenthetical - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accounts receivable, less allowance for doubtful accounts	$ 20,337	$ 20,205
Common Class A [Member]
Common Stock, Shares, Issued	25,007,469	24,966,035
Common Stock, Shares, Outstanding	24,586,408	24,835,804
Common Class B [Member]
Common Stock, Shares, Issued	5,091,968	5,089,532
Common Stock, Shares, Outstanding	5,091,968	5,089,532
Treasury Class A [Member]
Treasury Stock, Shares	421,061	130,231