Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Contract revenues	$ 168,638	$ 175,841	$ 516,185	$ 561,456
Type of Revenue [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
Costs of contract revenues	$ 132,357	$ 139,490	$ 423,906	$ 423,615
Type of Cost, Good or Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
Gross profit	$ 36,281	$ 36,351	$ 92,279	$ 137,841
General and administrative expenses	15,167	14,888	45,713	45,263
Proceeds from loss of use claim		(1,723)		(1,723)
Gain on sale of assets—net	(291)		(323)	(184)
Operating income	21,405	23,186	46,889	94,485
Interest expense—net	(4,214)	(6,719)	(17,457)	(20,074)
Other income (expense)	(204)	156	692	(400)
Income before income taxes	16,987	16,623	30,124	74,011
Income tax provision	(3,181)	(4,076)	(5,399)	(18,517)
Net income	$ 13,806	$ 12,547	$ 24,725	$ 55,494
Basic earnings per share	$ 0.21	$ 0.19	$ 0.38	$ 0.86
Basic weighted average shares	65,691	64,860	65,535	64,726
Diluted earnings per share	$ 0.21	$ 0.19	$ 0.37	$ 0.84
Diluted weighted average shares	66,311	65,894	66,246	65,861