Acquisitions - Narrative (Details) $ in Thousands	May 30, 2019 USD ($) store	Aug. 10, 2018 USD ($) store	Jan. 01, 2018 USD ($) store	Sep. 30, 2019 store	Jun. 30, 2019 store	Dec. 31, 2018 store	Sep. 30, 2018 store	Jun. 30, 2018 store	Dec. 31, 2017 store
Business Acquisition [Line Items]
Number of owned and franchised locations | store				1,899	1,859	1,742	1,646	1,608	1,518
Maine Acquisition
Business Acquisition [Line Items]
Number of owned and franchised locations | store	4
Acquisition, gross cash payments	$ 14,801
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