Segment Reporting (Schedule of Operating Profit by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information
Operating profit	$ 20,782	$ 65,657	$ 65,048	$ 113,412
Operating Segments | OEM Segment
Segment Reporting Information
Operating profit	1,763	52,679	44,952	93,087
Operating Segments | Aftermarket Segment
Segment Reporting Information
Operating profit	$ 19,019	$ 12,978	$ 20,096	$ 20,325