Revenue Recognition (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	$ 49,345,000	$ 45,760,000	$ 30,445,000	$ 26,157,000
Deferred Revenue, Current	20,510,000		12,569,000
Deferred Revenue, Noncurrent	$ 28,835,000		$ 17,876,000
Tires And Other | Transamerican Auto Parts | Minimum
Deferred Revenue Arrangement [Line Items]
Standard Product Warranty Time Period	2 years
Tires And Other | Transamerican Auto Parts | Maximum
Deferred Revenue Arrangement [Line Items]
Standard Product Warranty Time Period	5 years
Powertrains
Deferred Revenue Arrangement [Line Items]
Standard Product Warranty Time Period	5 years