Segment Information, Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Segment Unit	Sep. 30, 2015 USD ($)
Segment Information [Abstract]
Number of reportable segments | Segment			3
Segment Reporting Information [Line Items]
Net sales	$ 247,752	$ 211,350	$ 820,868	$ 768,141
Gross profit	$ 55,389	$ 45,138	$ 200,797	$ 173,417
Gross profit percent	22.40%	21.40%	24.50%	22.60%
Segment profit (loss)	$ 6,835	$ 1,958	$ 42,654	$ 28,532
Infrastructure Group [Member]
Segment Reporting Information [Line Items]
Number of business units | Unit			5
Number of business units that design, engineer, manufacture and market | Unit			3
Number of business units that operate as Company-owned dealers in foreign countries | Unit			2
Aggregate and Mining Group [Member]
Segment Reporting Information [Line Items]
Number of business units that design, engineer, manufacture and market | Unit			8
Energy Group [Member]
Segment Reporting Information [Line Items]
Number of business units that design, engineer, manufacture and market, through May 2015 | Unit			5
Number of business units that design, engineer, manufacture and market, June 2015 through July 2016 | Unit			4
Number of business units that design, engineer, manufacture and market, thereafter | Unit			5
Reportable Segments [Member]
Segment Reporting Information [Line Items]
Segment profit (loss)	6,704	994	$ 42,021	28,564
Reportable Segments [Member] | Infrastructure Group [Member]
Segment Reporting Information [Line Items]
Net sales	109,227	85,625	414,817	336,768
Gross profit	$ 24,929	$ 16,104	$ 101,349	$ 74,292
Gross profit percent	22.80%	18.80%	24.40%	22.10%
Segment profit (loss)	$ 9,858	$ 2,116	$ 51,394	$ 29,472
Reportable Segments [Member] | Aggregate and Mining Group [Member]
Segment Reporting Information [Line Items]
Net sales	85,819	80,549	277,393	285,790
Gross profit	$ 20,935	$ 19,226	$ 72,224	$ 70,182
Gross profit percent	24.40%	23.90%	26.00%	24.60%
Segment profit (loss)	$ 7,651	$ 3,790	$ 28,135	$ 25,441
Reportable Segments [Member] | Energy Group [Member]
Segment Reporting Information [Line Items]
Net sales	52,706	45,176	128,658	145,583
Gross profit	$ 9,473	$ 9,794	$ 27,069	$ 28,912
Gross profit percent	18.00%	21.70%	21.00%	19.90%
Segment profit (loss)	$ 805	$ 1,941	$ 3,237	$ 2,805
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	19,495	11,565	47,586	50,821
Segment profit (loss)	131	964	633	(32)
Intersegment Eliminations [Member] | Infrastructure Group [Member]
Segment Reporting Information [Line Items]
Net sales	5,324	5,839	13,009	17,633
Intersegment Eliminations [Member] | Aggregate and Mining Group [Member]
Segment Reporting Information [Line Items]
Net sales	10,063	4,604	20,859	19,223
Intersegment Eliminations [Member] | Energy Group [Member]
Segment Reporting Information [Line Items]
Net sales	4,108	1,122	13,718	13,965
Corporate [Member]
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Gross profit	$ 52	$ 14	$ 155	$ 31
Gross profit percent	0.00%	0.00%	0.00%	0.00%
Segment profit (loss)	$ (11,610)	$ (6,853)	$ (40,745)	$ (29,154)