Revenue Recognition (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Abstract]
Net sales		$ 1,171,599	$ 1,184,739	$ 1,147,431
Pellet Plant [Member]
Disaggregation of Revenue [Abstract]
Amount paid to customer	$ 68,000
Forgiveness of accounts receivable	$ 7,315
United States [Member]
Disaggregation of Revenue [Abstract]
Net sales		915,814
United States [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		695,573
United States [Member] | Pellet Plant Agreement Sale Reduction [Member]
Disaggregation of Revenue [Abstract]
Net sales		(75,315)
United States [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		234,351
United States [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		19,021
United States [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		15,583
United States [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		24,663
United States [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Net sales		1,938
International [Member]
Disaggregation of Revenue [Abstract]
Net sales		255,785
International [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		166,428
International [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		74,352
International [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		4,611
International [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		5,549
International [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		4,726
International [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Net sales		119
Infrastructure Group [Member]
Disaggregation of Revenue [Abstract]
Net sales		442,289
Infrastructure Group [Member] | Pellet Plant Agreement Sale Reduction [Member]
Disaggregation of Revenue [Abstract]
Net sales		(75,315)
Infrastructure Group [Member] | United States [Member]
Disaggregation of Revenue [Abstract]
Net sales		373,926
Infrastructure Group [Member] | United States [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		296,974
Infrastructure Group [Member] | United States [Member] | Pellet Plant Agreement Sale Reduction [Member]
Disaggregation of Revenue [Abstract]
Net sales		(75,315)
Infrastructure Group [Member] | United States [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		119,823
Infrastructure Group [Member] | United States [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		10,822
Infrastructure Group [Member] | United States [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		8,098
Infrastructure Group [Member] | United States [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		12,502
Infrastructure Group [Member] | United States [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Net sales		1,022
Infrastructure Group [Member] | International [Member]
Disaggregation of Revenue [Abstract]
Net sales		68,363
Infrastructure Group [Member] | International [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		43,516
Infrastructure Group [Member] | International [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		19,215
Infrastructure Group [Member] | International [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		3,152
Infrastructure Group [Member] | International [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		1,693
Infrastructure Group [Member] | International [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		1,043
Infrastructure Group [Member] | International [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Net sales		(256)
Aggregate and Mining Group [Member]
Disaggregation of Revenue [Abstract]
Net sales		453,164
Aggregate and Mining Group [Member] | United States [Member]
Disaggregation of Revenue [Abstract]
Net sales		302,372
Aggregate and Mining Group [Member] | United States [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		220,015
Aggregate and Mining Group [Member] | United States [Member] | Pellet Plant Agreement Sale Reduction [Member]
Disaggregation of Revenue [Abstract]
Net sales		0
Aggregate and Mining Group [Member] | United States [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		71,862
Aggregate and Mining Group [Member] | United States [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		1,844
Aggregate and Mining Group [Member] | United States [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		3,127
Aggregate and Mining Group [Member] | United States [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		6,265
Aggregate and Mining Group [Member] | United States [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Net sales		(741)
Aggregate and Mining Group [Member] | International [Member]
Disaggregation of Revenue [Abstract]
Net sales		150,792
Aggregate and Mining Group [Member] | International [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		98,604
Aggregate and Mining Group [Member] | International [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		44,609
Aggregate and Mining Group [Member] | International [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		1,069
Aggregate and Mining Group [Member] | International [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		2,948
Aggregate and Mining Group [Member] | International [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		3,266
Aggregate and Mining Group [Member] | International [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Net sales		296
Energy Group [Member]
Disaggregation of Revenue [Abstract]
Net sales		276,146
Energy Group [Member] | United States [Member]
Disaggregation of Revenue [Abstract]
Net sales		239,516
Energy Group [Member] | United States [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		178,584
Energy Group [Member] | United States [Member] | Pellet Plant Agreement Sale Reduction [Member]
Disaggregation of Revenue [Abstract]
Net sales		0
Energy Group [Member] | United States [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		42,666
Energy Group [Member] | United States [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		6,355
Energy Group [Member] | United States [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		4,358
Energy Group [Member] | United States [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		5,896
Energy Group [Member] | United States [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Net sales		1,657
Energy Group [Member] | International [Member]
Disaggregation of Revenue [Abstract]
Net sales		36,630
Energy Group [Member] | International [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		24,308
Energy Group [Member] | International [Member] | Parts and Component Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		10,528
Energy Group [Member] | International [Member] | Service and Equipment Installation Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		390
Energy Group [Member] | International [Member] | Used Equipment Sales [Member]
Disaggregation of Revenue [Abstract]
Net sales		908
Energy Group [Member] | International [Member] | Freight Revenue [Member]
Disaggregation of Revenue [Abstract]
Net sales		417
Energy Group [Member] | International [Member] | Other [Member]
Disaggregation of Revenue [Abstract]
Net sales		$ 79