Industry Segments (Details) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) Segment	Jun. 30, 2018 USD ($)
Segment Reporting Information, Profit (Loss) [Abstract]
Number of reportable operating segments | Segment				2
Net sales	[1]	$ 305,172	$ 286,636	$ 588,938	$ 548,462
Operating income		27,728	23,350	45,685	35,657
Intersegment Revenues [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net sales	[1]	0	0	0	0
Engine Management [Member] | Reportable Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net sales	[1]	218,042	203,429	431,231	402,917
Operating income		25,709	23,138	48,053	40,514
Engine Management [Member] | Intersegment Revenues [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net sales	[1]	4,921	4,981	10,270	10,972
Temperature Control [Member] | Reportable Segments [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net sales	[1]	84,406	80,370	153,330	140,601
Operating income		7,154	4,882	9,204	5,713
Temperature Control [Member] | Intersegment Revenues [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net sales	[1]	1,786	2,140	3,719	3,820
All Other [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net sales	[1]	2,724	2,837	4,377	4,944
Operating income		(5,135)	(4,670)	(11,572)	(10,570)
All Other [Member] | Intersegment Revenues [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net sales	[1]	$ (6,707)	$ (7,121)	$ (13,989)	$ (14,792)

[1] Segment net sales include intersegment sales in our Engine Management and Temperature Control segments.