Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Net sales	$ 113,822	$ 99,082
Gross profit	25,793	15,390
Operating Segments | Units
Segment Reporting Information [Line Items]
Net sales	107,068	92,975
Gross profit	26,543	16,540
Operating Segments | Parts
Segment Reporting Information [Line Items]
Net sales	6,911	6,287
Gross profit	3,684	3,029
Other
Segment Reporting Information [Line Items]
Net sales	(157)	(180)
Gross profit	(4,434)	(4,179)
Inter-segment
Segment Reporting Information [Line Items]
Net sales	7,922	7,284
Gross profit	$ 677	$ 795