CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Account Receivable, allowances aggregating	$ 31,426	$ 25,661
Closure and post-closure liabilities, current portion	7,229	4,999
Remedial liabilities, current portion	$ 13,166	$ 17,092
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares	80,000,000	80,000,000
Common stock, issued shares	57,593,201	58,903,482
Common stock, outstanding shares	57,593,201	58,903,482