Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
CONTRACT REVENUES	$ 726,149	$ 733,601	$ 711,518
Type of Revenue [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
COSTS OF CONTRACT REVENUES	$ 580,879	$ 562,373	$ 557,761
Type of Cost, Good or Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
GROSS PROFIT	$ 145,270	$ 171,228	$ 153,757
OPERATING EXPENSES:
GENERAL AND ADMINISTRATIVE EXPENSES	62,134	62,757	59,110
PROCEEDS FROM LOSS OF USE CLAIM		(1,723)	(4,619)
(GAIN) LOSS ON SALE OF ASSETS—Net	(294)	(1,571)	1,138
Total operating income	83,430	111,765	98,128
OTHER EXPENSE:
Interest expense—net	(21,601)	(26,585)	(27,524)
Other income	994	1,110	317
Total other expense	(20,607)	(25,475)	(27,207)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	62,823	86,290	70,921
INCOME TAX PROVISION	(13,391)	(20,187)	(15,253)
INCOME FROM CONTINUING OPERATIONS	49,432	66,103	55,668
Loss from discontinued operations, net of income taxes			(6,329)
NET INCOME	$ 49,432	$ 66,103	$ 49,339
Basic earnings per share attributable to income from continuing operations	$ 0.75	$ 1.02	$ 0.88
Basic loss per share attributable to loss on discontinued operations, net of income taxes			(0.10)
Basic earnings per share	$ 0.75	$ 1.02	$ 0.78
Basic weighted average shares	65,587	64,743	63,597
Diluted earnings per share attributable to income from continuing operations	$ 0.75	$ 1.00	$ 0.86
Diluted loss per share attributable to loss on discontinued operations, net of income taxes			(0.10)
Diluted earnings per share	$ 0.75	$ 1.00	$ 0.76
Diluted weighted average shares	66,301	65,872	65,042