Segment Information, Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) Businessunit Segment	Jun. 30, 2018 USD ($)
Segment Information [Abstract]
Number of reportable segments | Segment			3
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	$ 304,802	$ 272,528	$ 630,582	$ 597,981
Gross profit (loss)	83,450	1,108	159,976	79,113
Segment profit (loss)	23,361	(40,768)	$ 37,579	(20,552)
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	133,235	83,202	$ 288,229	230,296
Aggregate and Mining Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Number of business units | Businessunit			8
Net sales	106,837	116,297	$ 213,368	235,364
Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Number of business units | Businessunit			6
Net sales	64,730	73,029	$ 128,985	132,321
Corporate [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	0	0	0	0
Gross profit (loss)	$ 81	$ 75	$ 76	$ 223
Gross profit (loss) percent	0.00%	0.00%	0.00%	0.00%
Segment profit (loss)	$ (13,220)	$ 596	$ (26,690)	$ (10,652)
Reportable Segments [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	304,802	272,528	630,582	597,981
Gross profit (loss)	$ 83,450	$ 1,108	$ 159,976	$ 79,113
Gross profit (loss) percent	27.40%	0.40%	25.40%	13.20%
Segment profit (loss)	$ 22,852	$ (41,113)	$ 36,691	$ (19,788)
Reportable Segments [Member] | Infrastructure Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	133,235	83,202	288,229	230,296
Gross profit (loss)	$ 42,689	$ (47,817)	$ 78,196	$ (14,536)
Gross profit (loss) percent	32.00%	(57.50%)	27.10%	(6.30%)
Segment profit (loss)	$ 24,445	$ (62,734)	$ 39,683	$ (47,882)
Reportable Segments [Member] | Aggregate and Mining Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	106,837	116,297	213,368	235,364
Gross profit (loss)	$ 25,493	$ 29,042	$ 51,038	$ 58,331
Gross profit (loss) percent	23.90%	25.00%	23.90%	24.80%
Segment profit (loss)	$ 8,489	$ 12,548	$ 17,166	$ 25,658
Reportable Segments [Member] | Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	64,730	73,029	128,985	132,321
Gross profit (loss)	$ 15,187	$ 19,808	$ 30,666	$ 35,095
Gross profit (loss) percent	23.50%	27.10%	23.80%	26.50%
Segment profit (loss)	$ 3,138	$ 8,477	$ 6,532	$ 13,088
Intersegment Eliminations [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	12,726	15,196	26,575	32,512
Segment profit (loss)	509	345	888	(764)
Intersegment Eliminations [Member] | Infrastructure Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	2,849	3,370	4,920	11,641
Intersegment Eliminations [Member] | Aggregate and Mining Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	5,782	5,102	10,539	9,008
Intersegment Eliminations [Member] | Energy Group [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	4,095	6,724	11,116	11,863
Intersegment Eliminations [Member] | Corporate [Member]
Segment reporting, disclosure and reportable segments revenues and profits [Abstract]
Net sales	$ 0	$ 0	$ 0	$ 0