CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
CURRENT ASSETS:
Accounts receivable, allowance	$ 12,839	$ 12,375
PROPERTY, EQUIPMENT AND FACILITIES - accumulated depreciation and amortization	159,237	157,152
OTHER ASSETS:
Noncurrent receivables, allowance	$ 1,220	$ 977
STOCKHOLDERS' EQUITY:
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)	0	0
Preferred stock, shares outstanding (in shares)	0	0
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)	30,498,388	30,685,017
Common stock, shares outstanding (in shares)	30,498,388	30,685,017
Treasury stock, shares (in shares)	5,910,541	5,910,541