Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Abstract]
Total net sales	$ 304,802	$ 272,528	$ 630,582	$ 597,981
Domestic [Member]
Disaggregation of Revenue [Abstract]
Total net sales	246,213	203,386	509,042	473,464
Domestic [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	153,219	202,624	327,519	388,368
Domestic [Member] | Pellet Plant Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	20,000		20,000
Domestic [Member] | Pellet Plant Agreement Sale Charge [Member]
Disaggregation of Revenue [Abstract]
Total net sales		(75,315)		(75,315)
Domestic [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	54,783	59,059	128,440	129,321
Domestic [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	8,867	5,179	14,266	9,529
Domestic [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	3,390	2,804	6,566	6,007
Domestic [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	6,508	6,745	13,503	13,923
Domestic [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Total net sales	(554)	2,290	(1,252)	1,631
International [Member]
Disaggregation of Revenue [Abstract]
Total net sales	58,589	69,142	121,540	124,517
International [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	34,851	44,500	75,314	77,504
International [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	19,298	19,660	38,242	37,483
International [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	2,397	1,201	4,185	2,326
International [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	562	1,874	1,138	3,233
International [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	1,258	1,808	2,348	3,656
International [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Total net sales	223	99	313	315
Africa [Member]
Disaggregation of Revenue [Abstract]
Total net sales	8,827	10,834	15,918	20,876
Asia (excl. China, Japan and Korea) [Member]
Disaggregation of Revenue [Abstract]
Total net sales	2,816	1,342	4,947	2,186
Australia [Member]
Disaggregation of Revenue [Abstract]
Total net sales	7,156	7,929	15,969	13,897
Canada [Member]
Disaggregation of Revenue [Abstract]
Total net sales	14,020	20,963	37,013	35,072
Central America [Member]
Disaggregation of Revenue [Abstract]
Total net sales	2,602	3,772	6,152	7,325
China, Japan and Korea [Member]
Disaggregation of Revenue [Abstract]
Total net sales	440	3,561	2,580	4,217
Europe [Member]
Disaggregation of Revenue [Abstract]
Total net sales	12,982	8,610	19,472	19,071
Middle East [Member]
Disaggregation of Revenue [Abstract]
Total net sales	925	2,280	1,776	2,910
South America [Member]
Disaggregation of Revenue [Abstract]
Total net sales	7,581	9,367	14,635	18,234
West Indies [Member]
Disaggregation of Revenue [Abstract]
Total net sales	188	551	1,566	660
Other Foreign Countries [Member]
Disaggregation of Revenue [Abstract]
Total net sales	1,052	(67)	1,512	69
Total Foreign [Member]
Disaggregation of Revenue [Abstract]
Total net sales	58,589	69,142	121,540	124,517
Infrastructure Group [Member]
Disaggregation of Revenue [Abstract]
Total net sales	133,235	83,202	288,229	230,296
Infrastructure Group [Member] | Domestic [Member]
Disaggregation of Revenue [Abstract]
Total net sales	119,979	65,072	250,524	199,558
Infrastructure Group [Member] | Domestic [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	65,514	102,724	144,878	188,242
Infrastructure Group [Member] | Domestic [Member] | Pellet Plant Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	20,000		20,000
Infrastructure Group [Member] | Domestic [Member] | Pellet Plant Agreement Sale Charge [Member]
Disaggregation of Revenue [Abstract]
Total net sales		(75,315)		(75,315)
Infrastructure Group [Member] | Domestic [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	24,535	29,269	66,726	70,382
Infrastructure Group [Member] | Domestic [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	4,867	3,283	8,098	5,211
Infrastructure Group [Member] | Domestic [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	2,205	1,384	3,698	3,009
Infrastructure Group [Member] | Domestic [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	3,146	3,216	6,976	7,254
Infrastructure Group [Member] | Domestic [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Total net sales	(288)	511	148	775
Infrastructure Group [Member] | International [Member]
Disaggregation of Revenue [Abstract]
Total net sales	13,256	18,130	37,705	30,738
Infrastructure Group [Member] | International [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	5,219	12,040	21,671	17,955
Infrastructure Group [Member] | International [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	5,435	4,310	11,708	9,372
Infrastructure Group [Member] | International [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	2,084	644	3,448	1,457
Infrastructure Group [Member] | International [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	121	661	231	1,164
Infrastructure Group [Member] | International [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	391	429	630	683
Infrastructure Group [Member] | International [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Total net sales	6	46	17	107
Aggregate and Mining Group [Member]
Disaggregation of Revenue [Abstract]
Total net sales	106,837	116,297	213,368	235,364
Aggregate and Mining Group [Member] | Domestic [Member]
Disaggregation of Revenue [Abstract]
Total net sales	69,340	78,893	145,055	162,730
Aggregate and Mining Group [Member] | Domestic [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	46,887	57,989	102,091	121,483
Aggregate and Mining Group [Member] | Domestic [Member] | Pellet Plant Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	0		0
Aggregate and Mining Group [Member] | Domestic [Member] | Pellet Plant Agreement Sale Charge [Member]
Disaggregation of Revenue [Abstract]
Total net sales		0		0
Aggregate and Mining Group [Member] | Domestic [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	18,921	18,311	38,080	36,145
Aggregate and Mining Group [Member] | Domestic [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	2,431	564	3,056	890
Aggregate and Mining Group [Member] | Domestic [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	0	652	413	2,063
Aggregate and Mining Group [Member] | Domestic [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	1,801	1,912	3,396	3,720
Aggregate and Mining Group [Member] | Domestic [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Total net sales	(700)	(535)	(1,981)	(1,571)
Aggregate and Mining Group [Member] | International [Member]
Disaggregation of Revenue [Abstract]
Total net sales	37,497	37,404	68,313	72,634
Aggregate and Mining Group [Member] | International [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	24,416	23,385	43,465	45,712
Aggregate and Mining Group [Member] | International [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	11,438	12,070	21,616	22,359
Aggregate and Mining Group [Member] | International [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	308	328	700	640
Aggregate and Mining Group [Member] | International [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	371	630	837	1,486
Aggregate and Mining Group [Member] | International [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	762	967	1,430	2,297
Aggregate and Mining Group [Member] | International [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Total net sales	202	24	265	140
Energy Group [Member]
Disaggregation of Revenue [Abstract]
Total net sales	64,730	73,029	128,985	132,321
Energy Group [Member] | Domestic [Member]
Disaggregation of Revenue [Abstract]
Total net sales	56,894	59,421	113,463	111,176
Energy Group [Member] | Domestic [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	40,818	41,911	80,550	78,643
Energy Group [Member] | Domestic [Member] | Pellet Plant Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	0		0
Energy Group [Member] | Domestic [Member] | Pellet Plant Agreement Sale Charge [Member]
Disaggregation of Revenue [Abstract]
Total net sales		0		0
Energy Group [Member] | Domestic [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	11,327	11,479	23,634	22,794
Energy Group [Member] | Domestic [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	1,569	1,332	3,112	3,428
Energy Group [Member] | Domestic [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	1,185	768	2,455	935
Energy Group [Member] | Domestic [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	1,561	1,617	3,131	2,949
Energy Group [Member] | Domestic [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Total net sales	434	2,314	581	2,427
Energy Group [Member] | International [Member]
Disaggregation of Revenue [Abstract]
Total net sales	7,836	13,608	15,522	21,145
Energy Group [Member] | International [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	5,216	9,075	10,178	13,837
Energy Group [Member] | International [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	2,425	3,280	4,918	5,752
Energy Group [Member] | International [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	5	229	37	229
Energy Group [Member] | International [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Total net sales	70	583	70	583
Energy Group [Member] | International [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Total net sales	105	412	288	676
Energy Group [Member] | International [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Total net sales	$ 15	$ 29	$ 31	$ 68