BUSINESS COMBINATIONS - Summary of Purchase Price Paid for Acquisitions (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Purchase Price:
Cash used in acquisitions, net of cash acquired	$ 73,496	$ 58,176
Allocated as follows:
Excess purchase price allocated to goodwill	184,295		$ 162,734
Waste Collection Acquisitions
Purchase Price:
Cash used in acquisitions, net of cash acquired	71,038	57,824
Notes payable	2,714	0
Common stock	0	4,258
Other non-cash consideration	5,470	0
Contingent consideration and holdbacks	1,755	4,996
Total	80,977	67,078
Allocated as follows:
Current assets	1,935	2,968
Other non-current assets	367	0
Land	2,487	0
Buildings	5,422	7,539
Equipment	20,592	11,520
Intangible assets	31,171	20,300
Other liabilities, net	(3,040)	(2,443)
Deferred tax liability	(2,137)	(1,230)
Fair value of assets acquired and liabilities assumed	56,797	38,654
Excess purchase price allocated to goodwill	24,180	28,424
Common stock	$ 0	$ 4,258