Revenue - Revenue from External Customers by Geographic Areas (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Net sales	$ 456,255	$ 417,639
United States
Disaggregation of Revenue [Line Items]
Net sales	406,077	366,445
North America
Disaggregation of Revenue [Line Items]
Net sales	8,616	9,831
Pacific Rim
Disaggregation of Revenue [Line Items]
Net sales	25,457	25,869
Europe
Disaggregation of Revenue [Line Items]
Net sales	7,457	9,339
Other
Disaggregation of Revenue [Line Items]
Net sales	8,648	6,155
Power Systems
Disaggregation of Revenue [Line Items]
Net sales	123,132	149,282
Industrial
Disaggregation of Revenue [Line Items]
Net sales	153,289	131,026
Transportation
Disaggregation of Revenue [Line Items]
Net sales	$ 179,834	$ 137,331