Acquisition - Narrative (Details) $ in Thousands	Aug. 10, 2018 USD ($) store	Jan. 01, 2018 USD ($) store	Dec. 31, 2018 store	Dec. 31, 2017 store	Dec. 31, 2016 store	Dec. 31, 2015 store
Business Acquisition [Line Items]
Number of owned and franchised locations | store			1,742	1,518	1,313	1,124
Colorado Acquisition
Business Acquisition [Line Items]
Number of owned and franchised locations | store	4
Acquisition, gross cash payments	$ 17,249
Loss on reacquired franchise rights	10
Consideration transferred	$ 17,239
Long Island Acquisition
Business Acquisition [Line Items]
Number of owned and franchised locations | store		6
Acquisition, gross cash payments		$ 28,503
Loss on reacquired franchise rights		350
Consideration transferred		$ 28,153