CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenues	$ 743,290,000	$ 660,660,000	$ 599,309,000
Operating expenses:
Cost of operations	508,656,000	453,291,000	405,188,000
General and administration	92,782,000	84,791,000	79,243,000
Depreciation and amortization	79,790,000	70,508,000	62,102,000
Southbridge Landfill closure charge, net	2,709,000	8,054,000	65,183,000
Withdrawal costs - multiemployer pension plan	3,591,000	0	0
Expense from acquisition activities and other items	2,687,000	1,872,000	176,000
Contract settlement charge	0	2,100,000	0
Development project charge	0	311,000	0
Total operating expenses	690,215,000	620,927,000	611,892,000
Operating income (loss)	53,075,000	39,733,000	(12,583,000)
Other expense (income):
Interest income	(367,000)	(273,000)	(273,000)
Interest expense	25,102,000	26,294,000	25,160,000
Loss on debt extinguishment	0	7,352,000	517,000
Impairment of investments	0	1,069,000	0
Other income	(1,439,000)	(745,000)	(935,000)
Other expense, net	23,296,000	33,697,000	24,469,000
Income (loss) before income taxes	29,779,000	6,036,000	(37,052,000)
Benefit for income taxes	(1,874,000)	(384,000)	(15,253,000)
Net income (loss)	$ 31,653,000	$ 6,420,000	$ (21,799,000)
Basic earnings (loss) per common share:
Weighted average common shares outstanding	47,226	42,688	41,846
Basic earnings (loss) per common share (in dollars per share)	$ 0.67	$ 0.15	$ (0.52)
Diluted earnings (loss) per common share:
Weighted average common shares outstanding	47,966	44,168	41,846
Diluted earnings (loss) per common share (in dollars per share)	$ 0.66	$ 0.15	$ (0.52)