Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net sales	$ 116,700	$ 134,772	$ 125,596	$ 137,483	$ 122,574	$ 113,500	$ 119,437	$ 113,822	$ 514,551	$ 469,333	$ 433,947
Gross profit	$ 33,923	$ 40,848	$ 38,131	$ 42,947	$ 36,381	$ 27,410	$ 30,204	$ 25,430	155,849	119,425	103,533
Operating Segments | Units
Segment Reporting Information [Line Items]
Net sales									480,629	434,283	406,331
Gross profit									164,048	121,878	108,214
Operating Segments | Parts
Segment Reporting Information [Line Items]
Net sales									34,577	35,424	28,456
Gross profit									15,592	17,301	13,215
Other
Segment Reporting Information [Line Items]
Net sales									(655)	(374)	(840)
Gross profit									(23,791)	(19,754)	(17,896)
Inter-segment
Segment Reporting Information [Line Items]
Net sales									24,236	28,053	29,385
Gross profit									$ (1,461)	$ 985	$ 865