Basis and Summary of Significant Accounting Policies - Related Party Transactions (Details) $ in Millions |
3 Months Ended | 12 Months Ended | 36 Months Ended |
|---|---|---|---|
|
Mar. 31, 2019
USD ($)
lease
franchise
|
Dec. 31, 2018 |
Dec. 31, 2004
Property
|
|
| Related Party Transaction [Line Items] | |||
| Threshold Period Past Due for Write-off of Trade Accounts Receivable | 60 days | ||
| Additional number of businesses acquired | franchise | 2 | ||
| Related Party | |||
| Related Party Transaction [Line Items] | |||
| Sale leaseback, number of properties | Property | 21 | ||
| Number of capital leases | lease | 2 | ||
| Number of operating leases | lease | 4 | ||
| Capital leases, annual rental payments | $ | $ 0.1 | ||
| Interest rate in the leases | 9.70% | ||
| Operating leases, annual rental payments | $ | $ 0.2 |