CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Account receivable, allowances aggregating	$ 29,249	$ 31,426
Closure and post-closure liabilities, current portion	6,220	7,229
Remedial liabilities, current portion	$ 13,796	$ 13,166
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	80,000,000	80,000,000
Common stock, issued shares (in shares)	57,297,978	57,593,201
Common stock, outstanding shares (in shares)	57,297,978	57,593,201