Business and Summary of Significant Accounting Policies - Summary of Goodwill by Reporting Unit (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) segments	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Goodwill [Line Items]
Number of operating segments | segments	3
Goodwill	$ 622,948	$ 526,723	$ 539,475
Progressive Leasing
Goodwill [Line Items]
Goodwill	288,801	288,801	290,605
DAMI
Goodwill [Line Items]
Goodwill	$ 0	$ 0	$ 290