Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets:
Allowance for doubtful accounts	$ 9,348	$ 9,625
Class A Non-Voting
Shareholders' Investment:
Common stock, par value (in usd per share)	$ 1	$ 1
Common shares authorized (shares)	50,000,000	50,000,000
Common shares issued (shares)	30,610,000	30,927,000
Common shares outstanding (shares)	30,610,000	30,927,000
Class B Voting
Shareholders' Investment:
Common stock, par value (in usd per share)	$ 1	$ 1
Common shares authorized (shares)	50,000,000	50,000,000
Common shares issued (shares)	22,671,000	24,408,000
Common shares outstanding (shares)	22,671,000	24,408,000