Summary of Significant Accounting Policies Other Intangible Assets and Deferred Financing Costs (Details)	12 Months Ended
	Dec. 31, 2017
Computer software | Minimum
Finite-Lived Intangible Assets
Finite-Lived Intangible Asset, Useful Life	3 years
Computer software | Maximum
Finite-Lived Intangible Assets
Finite-Lived Intangible Asset, Useful Life	5 years
Reacquired rights under franchise agreements | Minimum
Finite-Lived Intangible Assets
Finite-Lived Intangible Asset, Useful Life	4 years
Reacquired rights under franchise agreements | Maximum
Finite-Lived Intangible Assets
Finite-Lived Intangible Asset, Useful Life	20 years
Franchise agreements
Finite-Lived Intangible Assets
Finite-Lived Intangible Asset, Useful Life	20 years