Corporate-owned and Franchisee-owned Stores - Schedule of Changes in Corporate-owned and Franchisee-owned Stores (Detail) - Store		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Franchisor Disclosure [Line Items]
Stores operated at beginning of period		1,124	918	749
New stores opened		195	209	171
Stores debranded, sold or consolidated	[1]	(6)	(3)	(2)
Stores operated at end of period		1,313	1,124	918
Franchisee-Owned Stores [Member]
Franchisor Disclosure [Line Items]
Stores operated at beginning of period		1,066	863	704
New stores opened		195	206	169
Stores debranded, sold or consolidated	[1]	(6)	(3)	(10)
Stores operated at end of period		1,255	1,066	863
Corporate-Owned Stores [Member]
Franchisor Disclosure [Line Items]
Stores operated at beginning of period		58	55	45
New stores opened			3	2
Stores acquired from franchisees				8
Stores operated at end of period		58	58	55

[1] The term “debrand” refers to a franchisee-owned store whose right to use the Planet Fitness brand and marks has been terminated in accordance with the franchise agreement. We retain the right to prevent debranded stores from continuing to operate as fitness centers. The term “consolidated” refers to the combination of a franchisee’s store with another store located in close proximity with our prior approval. This often coincides with an enlargement, re-equipment and/or refurbishment of the remaining store.