Condensed Consolidated Balance Sheets Parenthetical - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts receivable, less allowance for doubtful accounts	$ 23,147	$ 26,713
Common Class A [Member]
Common Stock, Shares, Issued	24,942,773	24,884,265
Common Stock, Shares, Outstanding	24,834,725	24,704,772
Common Class B [Member]
Common Stock, Shares, Issued	5,100,137	5,096,421
Common Stock, Shares, Outstanding	5,100,137	5,095,504
Treasury Class A [Member]
Treasury Stock, Shares	108,048	179,493
Treasury Class B [Member]
Treasury Stock, Shares	0	917