Summary of Significant Accounting Policies Corporate Structure (Details)	Dec. 31, 2017 countries Restaurant
Franchisor Disclosure
Number of Restaurants	6,634
Entity Operated Units
Franchisor Disclosure
Number of Restaurants	337
Franchised Units
Franchisor Disclosure
Number of Restaurants	6,297
Other International | Franchised Units
Franchisor Disclosure
Number of Countries Entity Operates | countries	29