SEGMENT REPORTING - Summary of Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 202,667	$ 198,547	$ 574,344	$ 549,670
Depreciation and amortization	23,799	20,940	67,281	58,144
Operating Income (Loss)	20,633	18,485	45,089	38,471
Total assets	994,255	935,780	994,255	935,780	$ 932,182
Operating | Eastern
Segment Reporting Information [Line Items]
Revenues	58,323	59,675	161,803	163,748
Depreciation and amortization	6,659	6,386	18,956	18,014
Operating Income (Loss)	3,683	2,121	9,023	5,722
Total assets	215,639	209,123	215,639	209,123
Operating | Western
Segment Reporting Information [Line Items]
Revenues	94,728	93,291	267,218	253,190
Depreciation and amortization	15,000	12,617	41,847	34,264
Operating Income (Loss)	15,344	15,161	32,849	30,905
Total assets	635,153	596,918	635,153	596,918
Operating | Resource Solutions
Segment Reporting Information [Line Items]
Revenues	49,616	45,581	145,323	132,732
Depreciation and amortization	1,544	1,349	4,692	3,946
Operating Income (Loss)	2,204	2,223	5,008	4,228
Total assets	89,870	92,612	89,870	92,612
Corporate entities
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Depreciation and amortization	596	588	1,786	1,920
Operating Income (Loss)	(598)	(1,020)	(1,791)	(2,384)
Total assets	53,593	37,127	53,593	37,127
Inter-company revenues
Segment Reporting Information [Line Items]
Revenues	(48,759)	(45,005)	(134,342)	(120,297)
Inter-company revenues | Eastern
Segment Reporting Information [Line Items]
Revenues	(14,261)	(15,156)	(39,936)	(40,606)
Inter-company revenues | Western
Segment Reporting Information [Line Items]
Revenues	(31,692)	(27,057)	(86,259)	(71,772)
Inter-company revenues | Resource Solutions
Segment Reporting Information [Line Items]
Revenues	$ (2,806)	$ (2,792)	$ (8,147)	$ (7,919)