Corporate-Owned and Franchisee-Owned Stores - Schedule of Changes in Corporate-owned and Franchisee-owned Stores (Detail) - Store	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Number Of Stores [Roll Forward]
Stores operated at beginning of period	1,565	1,367	1,518	1,313
New stores opened	44	37	91	91
Stores acquired, debranded, sold or consolidated	(1)	(1)	(1)	(1)
Stores operated at end of period	1,608	1,403	1,608	1,403
Franchisee-Owned Stores
Number Of Stores [Roll Forward]
Stores operated at beginning of period	1,497	1,309	1,456	1,255
New stores opened	44	37	91	91
Stores acquired, debranded, sold or consolidated	(1)	(1)	(7)	(1)
Stores operated at end of period	1,540	1,345	1,540	1,345
Corporate-Owned Stores
Number Of Stores [Roll Forward]
Stores operated at beginning of period	68	58	62	58
New stores opened	0	0	0	0
Stores acquired from franchisees	0	0	6	0
Stores operated at end of period	68	58	68	58