Warranty Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Warranty liability
Period of warranty history used in estimating warranty costs	5 years
Other long-term liabilities	$ 14,856	$ 17,004
Accrued expenses and other current liabilities	23,306	21,004
Company's warranty liability:
Balance at the beginning of the period	5,677	6,160	$ 7,423
Warranty provision	4,076	2,506	2,452
Claims paid/settlements	(3,579)	(3,054)	(3,750)
Balance at the end of the period	6,174	5,677	6,160
Warranty Reserves
Warranty liability
Other long-term liabilities	2,512	2,415
Accrued expenses and other current liabilities	$ 3,662	3,262
Henderson
Company's warranty liability:
Establish warranty provision for acquired companies		$ 65
Dejana
Company's warranty liability:
Establish warranty provision for acquired companies			$ 35
Snow and ice control equipment
Warranty liability
Warranty period	2 years
Parts and accessories
Warranty liability
Warranty period	1 year
Certain snowplows
Warranty liability
Warranty period	1 year