CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
CURRENT ASSETS:
Accounts receivable, allowance	$ 27,545	$ 26,837
PROPERTY, EQUIPMENT AND FACILITIES - accumulated depreciation and amortization	150,597	153,335
OTHER ASSETS:
Noncurrent receivables, allowance	$ 4,513	$ 5,084
STOCKHOLDERS' EQUITY:
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	27,260,154	27,000,687
Common stock, shares outstanding (in shares)	27,260,154	27,000,687
Treasury stock, shares (in shares)	5,910,541	5,910,541
Series A Convertible Preferred Stock [Member]
SERIES A CONVERTIBLE PREFERRED STOCK
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	12,700	12,700
Preferred stock, shares outstanding (in shares)	12,700	12,700