Summary of Significant Accounting Policies - Revenue From Contracts With Customers (Details) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Jan. 01, 2018	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Franchise Revenue		$ 5,611,000	$ 5,783,000	$ 19,065,000	$ 19,704,000
Operating Income Loss		12,808,000	$ 21,142,000	51,058,000	$ 57,447,000
Assets		$ 448,086,000		$ 448,086,000				$ 437,153,000
Accounting Standards Update 2014-09 | Scenario, Forecast
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with Customer, Asset, Net							$ 4,000,000
Accounting Standards Update 2014-09 | Scenario, Forecast | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase (Decrease) in Deferred Revenue and Customer Advances and Deposits	$ (26,000,000)
Maximum | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Franchise Revenue						$ (2,000,000)
Operating Income Loss						$ (2,000,000)