Organization and Summary of Significant Accounting Policies (Details 3) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finance and Insurance Sales
Aggregate reserves relating to chargeback activity	$ 23.8	$ 25.8
Defined Contribution Plans
Expense incurred relating to defined contribution plans	16.0	17.7	$ 15.1
Advertising
Net advertising costs	101.0	93.7	81.1
Reimbursement of advertising expense	17.2	14.3	$ 13.1
Self Insurance
Aggregate reserves relating to retained risk	$ 26.4	$ 24.6
Earnings Per Share
Weighted average number of common shares outstanding	89,759,626	90,318,839	90,273,747
Effect of non-participatory equity compensation (in shares)		36,000	56,874
Weighted average number of common shares outstanding, including effect of dilutive securities	89,759,626	90,354,839	90,330,621

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