GOODWILL AND INTANGIBLE ASSETS - Components of Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 36,179	$ 33,665
Less accumulated amortization	(28,030)	(25,969)
Intangible assets, net	8,149	7,696
Intangible amortization expenses	2,061	2,141	$ 2,567
Covenants Not-to-Compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets	18,092	17,594
Less accumulated amortization	(16,851)	(16,402)
Intangible assets, net	1,241	1,192
Client Lists
Finite-Lived Intangible Assets [Line Items]
Intangible assets	18,087	16,071
Less accumulated amortization	(11,179)	(9,567)
Intangible assets, net	$ 6,908	$ 6,504