Restructuring and Asset Impairment Charges - Restructuring Costs (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Impairment of a Company plane and costs associated with repairs	$ 2,612,000		$ 2,612,000
Goodwill impairment related to mobile asphalt equipment operations	0		1,600,000
Severance pay associated with workforce reductions at multiple sites	742,000		1,464,000
Restructuring and asset impairment charges	5,994,000	$ 44,000	8,705,000	$ 556,000
Mobile Asphalt Equipment
Restructuring Cost and Reserve [Line Items]
Goodwill impairment related to mobile asphalt equipment operations	0		1,646,000
AMM Operations
Restructuring Cost and Reserve [Line Items]
Business Exit Costs	285,000		285,000
Facility Closing | Mequon Site Closing
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	1,389,000		1,389,000
Facility Closing | Albuquerque Site Closing
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	750,000		1,093,000
Other Restructuring
Restructuring Cost and Reserve [Line Items]
Business Exit Costs	$ 216,000		$ 216,000