Segment Information, Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) Businessunit Segment	Sep. 30, 2018 USD ($)
Segment Information [Abstract]
Number of reportable segments | Segment			3
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	$ 255,807	$ 256,613	$ 886,389	$ 854,595
Gross profit	51,860	58,284	212,027	137,398
Restructuring charges	875	0	1,431	0
Segment profit (loss)	2,955	6,903	$ 40,535	(13,649)
Infrastructure Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Number of business units | Businessunit			5
Number of business units which design, engineer, manufacture and market product lines | Businessunit			3
Number of business units that operate as Company-owned dealers | Businessunit			2
Net sales	88,219	87,063	$ 376,448	317,359
Aggregate and Mining Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Number of business units | Businessunit			8
Net sales	99,617	101,735	$ 312,985	337,100
Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Number of business units | Businessunit			6
Net sales	67,971	67,815	$ 196,956	200,136
Corporate [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	0	0	0	0
Gross profit	$ 76	$ 66	$ 152	$ 292
Gross profit percent	0.00%	0.00%	0.00%	0.00%
Restructuring charges	$ 0		$ 0
Segment profit (loss)	(7,732)	$ (9,778)	(34,422)	$ (20,428)
Reportable Segments [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	255,807	256,613	886,389	854,595
Gross profit	$ 51,860	$ 58,284	$ 212,027	$ 137,398
Gross profit percent	20.30%	22.70%	23.90%	16.10%
Restructuring charges	$ 875		$ 1,431
Segment profit (loss)	2,745	$ 7,312	39,436	$ (12,474)
Reportable Segments [Member] | Infrastructure Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	88,219	87,063	376,448	317,359
Gross profit	$ 15,406	$ 18,642	$ 93,792	$ 4,105
Gross profit percent	17.50%	21.40%	24.90%	1.30%
Restructuring charges	$ 875		$ 1,431
Segment profit (loss)	(419)	$ 4,761	39,264	$ (43,121)
Reportable Segments [Member] | Aggregate and Mining Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	99,617	101,735	312,985	337,100
Gross profit	$ 20,837	$ 24,294	$ 71,876	$ 82,625
Gross profit percent	20.90%	23.90%	23.00%	24.50%
Restructuring charges	$ 0		$ 0
Segment profit (loss)	5,803	$ 9,011	22,969	$ 34,669
Reportable Segments [Member] | Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	67,971	67,815	196,956	200,136
Gross profit	$ 15,541	$ 15,282	$ 46,207	$ 50,376
Gross profit percent	22.90%	22.50%	23.50%	25.20%
Restructuring charges	$ 0		$ 0
Segment profit (loss)	5,093	$ 3,318	11,625	$ 16,406
Intersegment Eliminations [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	11,227	12,699	37,802	45,211
Segment profit (loss)	210	(409)	1,099	(1,175)
Intersegment Eliminations [Member] | Infrastructure Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	3,273	6,424	8,193	18,065
Intersegment Eliminations [Member] | Aggregate and Mining Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	4,842	4,300	15,381	13,308
Intersegment Eliminations [Member] | Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	3,112	1,975	14,228	13,838
Intersegment Eliminations [Member] | Corporate [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	$ 0	$ 0	$ 0	$ 0