Segment Information, Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Segment Businessunit	Sep. 30, 2017 USD ($)
Segment Information [Abstract]
Number of reportable segments | Segment			3
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	$ 256,613	$ 252,054	$ 854,595	$ 872,364
Gross profit	58,284	39,084	137,398	180,379
Segment profit (loss)	6,903	(2,703)	$ (13,649)	26,736
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	87,063		$ 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	101,735		$ 337,100
Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Number of business units | Businessunit			6
Net sales	67,815		$ 200,136
Corporate [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	0	0	0	0
Gross profit	$ 66	$ 51	$ 292	$ 160
Gross profit percent	0.00%	0.00%	0.00%	0.00%
Segment profit (loss)	$ (9,778)	$ (2,975)	$ (20,428)	$ (27,666)
Reportable Segments [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	256,613	252,054	854,595	872,364
Gross profit	$ 58,284	$ 39,084	$ 137,398	$ 180,379
Gross profit percent	22.70%	15.50%	16.10%	20.70%
Segment profit (loss)	$ 7,312	$ (1,479)	$ (12,474)	$ 27,594
Reportable Segments [Member] | Infrastructure Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	87,063	98,676	317,359	407,025
Gross profit	$ 18,642	$ 1,773	$ 4,105	$ 66,394
Gross profit percent	21.40%	1.80%	1.30%	16.30%
Segment profit (loss)	$ 4,761	$ (12,529)	$ (43,121)	$ 15,545
Reportable Segments [Member] | Aggregate and Mining Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	101,735	99,474	337,100	307,205
Gross profit	$ 24,294	$ 23,838	$ 82,625	$ 74,652
Gross profit percent	23.90%	24.00%	24.50%	24.30%
Segment profit (loss)	$ 9,011	$ 9,565	$ 34,669	$ 29,360
Reportable Segments [Member] | Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	67,815	53,904	200,136	158,134
Gross profit	$ 15,282	$ 13,422	$ 50,376	$ 39,173
Gross profit percent	22.50%	24.90%	25.20%	24.80%
Segment profit (loss)	$ 3,318	$ 4,460	$ 16,406	$ 10,355
Intersegment Eliminations [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	12,699	18,219	45,211	48,737
Segment profit (loss)	(409)	(1,224)	(1,175)	(858)
Intersegment Eliminations [Member] | Infrastructure Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	6,424	9,041	18,065	17,500
Intersegment Eliminations [Member] | Aggregate and Mining Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	4,300	3,551	13,308	13,003
Intersegment Eliminations [Member] | Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	1,975	5,627	13,838	18,234
Intersegment Eliminations [Member] | Corporate [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	$ 0	$ 0	$ 0	$ 0