Segment Reporting (Schedule of Operating Profit by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information
Operating profit	$ 65,657	$ 64,088	$ 113,412	$ 123,908
Operating Segments | OEM Segment
Segment Reporting Information
Operating profit	52,679	53,591	93,087	107,531
Operating Segments | Aftermarket Segment
Segment Reporting Information
Operating profit	$ 12,978	$ 10,497	$ 20,325	$ 16,377