CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowances (in dollars)	$ 7,736	$ 7,851
Other accounts receivable, allowances (in dollars)	$ 662	$ 660
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares	70,000,000	70,000,000
Common stock, issued shares	29,057,374	29,045,309
Treasury stock, at cost, shares	3,671,861	3,656,938