Organization and Summary of Significant Accounting Policies - Revenue, Defined Contrib. Plans, Advertising, Self-Insurance (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dealership Finance and Insurance Sales
Aggregate reserves relating to chargeback activity	$ 26,600	$ 26,000
Defined Contribution Plans
Expense incurred relating to defined contribution plans	29,400	24,800	$ 16,800
Advertising
Net advertising costs	112,600	115,300	115,800
Reimbursement of advertising expense	19,200	19,300	$ 18,600
Self Insurance
Aggregate reserves relating to retained risk	$ 28,600	$ 31,300

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Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

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