Basis and Summary of Significant Accounting Policies - Debt (Details) - USD ($) $ in Thousands |
Oct. 23, 2018 |
Sep. 30, 2018 |
Dec. 31, 2017 |
|---|---|---|---|
| Subsequent Event [Line Items] | |||
| Principal balance on term loan | $ 297,340 | $ 368,798 | |
| Loan facility to franchisees, maximum commitment amount | $ 85,000 | ||
| Subsequent Event | |||
| Subsequent Event [Line Items] | |||
| Loan facility to franchisees, maximum commitment amount | $ 55,000 | ||
| Unsecured Debt | Subsequent Event | Term Loan | |||
| Subsequent Event [Line Items] | |||
| Line of credit, maximum borrowing capacity | 225,000 | ||
| Principal balance on term loan | $ 87,500 |