CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Account receivable, allowances aggregating	$ 42,781	$ 38,711
Closure and post-closure liabilities, current portion	4,333	7,283
Remedial liabilities, current portion	$ 11,898	$ 16,018
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	80,000,000	80,000,000
Common stock, issued shares (in shares)	55,554,925	55,797,734
Common stock, outstanding shares (in shares)	55,554,925	55,797,734