Quarterly Financial Information Quarterly Financial Information By Segment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 346,544	$ 291,699	$ 264,086	$ 223,949	$ 255,175	$ 291,266	$ 268,734	$ 222,492	$ 1,126,278	$ 1,037,667	$ 957,958
Acquisition related costs	(2,153)	(1,896)	(262)	0					(4,311)	0	0
Operating income	9,732	12,115	11,184	4,720	9,410	14,373	12,149	6,679	37,751	42,611	26,176
Heavy Civil Construction
Segment Reporting Information [Line Items]
Revenues	190,690	218,894	200,236	150,505	190,443	222,299	194,174	158,722	760,325	765,638	801,652
Operating income	(7,704)	7,420	5,747	(2,147)	4,245	7,385	4,322	1,092	3,316	17,044	8,246
Specialty Service
Segment Reporting Information [Line Items]
Revenues	121,388	32,863	27,894	30,679	30,460	32,245	29,109	28,519	212,824	120,333	48,314
Operating income	14,923	1,371	865	1,048	983	1,647	1,480	519	18,207	4,629	2,284
Residential
Segment Reporting Information [Line Items]
Revenues	34,466	39,942	35,956	42,765	34,272	36,722	45,451	35,251	153,129	151,696	107,992
Operating income	4,666	5,220	4,834	5,819	$ 4,182	$ 5,341	$ 6,347	$ 5,068	20,539	20,938	15,646
Operating Segments
Segment Reporting Information [Line Items]
Operating income	$ 11,885	$ 14,011	$ 11,446	$ 4,720					$ 42,062	$ 42,611	$ 26,176

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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