Shareholders' Equity (Shares Issued And Shares Surrendered To Satisfy Tax Withholdings In Connection With Restricted Stock And Restricted Stock Units) (Details) - Restricted Stock And Restricted Stock Units [Member] - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued (in shares)	112,824	0
Shares surrendered to AutoNation to satisfy tax withholding obligations (in shares)	45,690	8,124