Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Net sales	$ 75,498	$ 77,029	$ 190,311	$ 190,281
Remaining performance obligation	1,100		1,100
Change In Contract With Customer Liability [Roll Forward]
Balance, beginning of period	693	1,066	1,084	1,096
Cash additions	304	314	993	1,060
Revenue recognition	(249)	(424)	(1,329)	(1,200)
Balance, end of period	748	956	748	956
United States
Disaggregation of Revenue [Line Items]
Net sales	65,498	66,731	169,079	167,768
Canada
Disaggregation of Revenue [Line Items]
Net sales	3,283	3,597	9,066	10,717
All other
Disaggregation of Revenue [Line Items]
Net sales	6,717	6,701	12,166	11,796
Product sales
Disaggregation of Revenue [Line Items]
Net sales	71,470	73,399	181,220	181,241
Extended warranties and services
Disaggregation of Revenue [Line Items]
Net sales	1,737	2,061	5,219	5,862
Other
Disaggregation of Revenue [Line Items]
Net sales	2,291	$ 1,569	3,872	$ 3,178
Retail Orders
Disaggregation of Revenue [Line Items]
Remaining performance obligation	600		600
Direct Orders
Disaggregation of Revenue [Line Items]
Remaining performance obligation	$ 600		$ 600