Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Disaggregation of Revenue [Abstract]
Net sales	$ 265,299	$ 304,802	$ 554,147	$ 630,582
Contract assets	25		25		$ 4,700
Contract liabilities	5,100		5,100		6,500
Extended Warranty Revenue
Disaggregation of Revenue [Abstract]
Deferred revenue	3,400		3,400		3,500
United States
Disaggregation of Revenue [Abstract]
Net sales	221,519	246,213	455,401	509,042
United States | Equipment sales
Disaggregation of Revenue [Abstract]
Net sales	147,883	153,219	289,599	327,519
United States | Pellet plant sales
Disaggregation of Revenue [Abstract]
Net sales		20,000		20,000
United States | Parts and component sales
Disaggregation of Revenue [Abstract]
Net sales	53,599	54,783	124,716	128,440
United States | Service and equipment installation revenue
Disaggregation of Revenue [Abstract]
Net sales	6,579	8,867	13,768	14,266
United States | Used equipment sales
Disaggregation of Revenue [Abstract]
Net sales	7,561	3,390	14,721	6,566
United States | Freight revenue
Disaggregation of Revenue [Abstract]
Net sales	5,991	6,508	13,348	13,503
United States | Other
Disaggregation of Revenue [Abstract]
Net sales	(94)	(554)	(751)	(1,252)
Canada
Disaggregation of Revenue [Abstract]
Net sales	12,997	14,020	27,661	37,013
Australia
Disaggregation of Revenue [Abstract]
Net sales	5,540	7,156	11,335	15,969
Africa
Disaggregation of Revenue [Abstract]
Net sales	4,168	8,827	10,799	15,918
South America
Disaggregation of Revenue [Abstract]
Net sales	11,164	7,581	19,960	14,635
Europe
Disaggregation of Revenue [Abstract]
Net sales	4,831	12,982	14,206	19,472
Central America
Disaggregation of Revenue [Abstract]
Net sales	917	2,602	2,307	6,152
International
Disaggregation of Revenue [Abstract]
Net sales	43,780	58,589	98,746	121,540
International | Equipment sales
Disaggregation of Revenue [Abstract]
Net sales	28,001	34,851	61,865	75,314
International | Parts and component sales
Disaggregation of Revenue [Abstract]
Net sales	12,791	19,298	30,382	38,242
International | Service and equipment installation revenue
Disaggregation of Revenue [Abstract]
Net sales	1,163	2,397	2,225	4,185
International | Used equipment sales
Disaggregation of Revenue [Abstract]
Net sales	1,099	562	2,451	1,138
International | Freight revenue
Disaggregation of Revenue [Abstract]
Net sales	624	1,258	1,533	2,348
International | Other
Disaggregation of Revenue [Abstract]
Net sales	102	223	290	313
China, Japan & Korea
Disaggregation of Revenue [Abstract]
Net sales	1,777	440	4,047	2,580
Asia (excl. China, Japan & Korea)
Disaggregation of Revenue [Abstract]
Net sales	1,159	2,816	1,594	4,947
West Indies
Disaggregation of Revenue [Abstract]
Net sales	56	188	4,812	1,566
Middle East
Disaggregation of Revenue [Abstract]
Net sales	1,167	925	2,016	1,776
Other
Disaggregation of Revenue [Abstract]
Net sales	4	1,052	9	1,512
Total foreign
Disaggregation of Revenue [Abstract]
Net sales	43,780	58,589	98,746	121,540
Infrastructure Solutions
Disaggregation of Revenue [Abstract]
Net sales	181,851	197,965	384,469	417,214
Infrastructure Solutions | One Large Order
Disaggregation of Revenue [Abstract]
Contract assets					$ 7,200
Infrastructure Solutions | United States
Disaggregation of Revenue [Abstract]
Net sales	158,462	176,873	331,307	363,987
Infrastructure Solutions | United States | Equipment sales
Disaggregation of Revenue [Abstract]
Net sales	104,640	106,332	205,059	225,428
Infrastructure Solutions | United States | Pellet plant sales
Disaggregation of Revenue [Abstract]
Net sales		20,000		20,000
Infrastructure Solutions | United States | Parts and component sales
Disaggregation of Revenue [Abstract]
Net sales	35,860	35,862	88,501	90,360
Infrastructure Solutions | United States | Service and equipment installation revenue
Disaggregation of Revenue [Abstract]
Net sales	6,181	6,436	12,943	11,210
Infrastructure Solutions | United States | Used equipment sales
Disaggregation of Revenue [Abstract]
Net sales	7,148	3,390	14,308	6,153
Infrastructure Solutions | United States | Freight revenue
Disaggregation of Revenue [Abstract]
Net sales	4,578	4,707	10,626	10,107
Infrastructure Solutions | United States | Other
Disaggregation of Revenue [Abstract]
Net sales	55	146	(130)	729
Infrastructure Solutions | International
Disaggregation of Revenue [Abstract]
Net sales	23,389	21,092	53,162	53,227
Infrastructure Solutions | International | Equipment sales
Disaggregation of Revenue [Abstract]
Net sales	15,565	10,435	34,989	31,849
Infrastructure Solutions | International | Parts and component sales
Disaggregation of Revenue [Abstract]
Net sales	5,902	7,860	14,236	16,626
Infrastructure Solutions | International | Service and equipment installation revenue
Disaggregation of Revenue [Abstract]
Net sales	668	2,089	1,510	3,485
Infrastructure Solutions | International | Used equipment sales
Disaggregation of Revenue [Abstract]
Net sales	814	191	1,420	301
Infrastructure Solutions | International | Freight revenue
Disaggregation of Revenue [Abstract]
Net sales	378	496	944	918
Infrastructure Solutions | International | Other
Disaggregation of Revenue [Abstract]
Net sales	62	21	63	48
Materials Solutions
Disaggregation of Revenue [Abstract]
Net sales	83,448	106,837	169,678	213,368
Materials Solutions | United States
Disaggregation of Revenue [Abstract]
Net sales	63,057	69,340	124,094	145,055
Materials Solutions | United States | Equipment sales
Disaggregation of Revenue [Abstract]
Net sales	43,243	46,887	84,540	102,091
Materials Solutions | United States | Pellet plant sales
Disaggregation of Revenue [Abstract]
Net sales		0		0
Materials Solutions | United States | Parts and component sales
Disaggregation of Revenue [Abstract]
Net sales	17,739	18,921	36,215	38,080
Materials Solutions | United States | Service and equipment installation revenue
Disaggregation of Revenue [Abstract]
Net sales	398	2,431	825	3,056
Materials Solutions | United States | Used equipment sales
Disaggregation of Revenue [Abstract]
Net sales	413	0	413	413
Materials Solutions | United States | Freight revenue
Disaggregation of Revenue [Abstract]
Net sales	1,413	1,801	2,722	3,396
Materials Solutions | United States | Other
Disaggregation of Revenue [Abstract]
Net sales	(149)	(700)	(621)	(1,981)
Materials Solutions | International
Disaggregation of Revenue [Abstract]
Net sales	20,391	37,497	45,584	68,313
Materials Solutions | International | Equipment sales
Disaggregation of Revenue [Abstract]
Net sales	12,436	24,416	26,876	43,465
Materials Solutions | International | Parts and component sales
Disaggregation of Revenue [Abstract]
Net sales	6,889	11,438	16,146	21,616
Materials Solutions | International | Service and equipment installation revenue
Disaggregation of Revenue [Abstract]
Net sales	495	308	715	700
Materials Solutions | International | Used equipment sales
Disaggregation of Revenue [Abstract]
Net sales	285	371	1,031	837
Materials Solutions | International | Freight revenue
Disaggregation of Revenue [Abstract]
Net sales	246	762	589	1,430
Materials Solutions | International | Other
Disaggregation of Revenue [Abstract]
Net sales	$ 40	$ 202	$ 227	$ 265