Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Liability payable under tax benefit obligations	$ 55,478		$ 55,478		$ 59,458
Administrative fees charged	1,388	$ 2,369	4,060	$ 4,235
Planet Fitness NAF, LLC
Related Party Transaction [Line Items]
Administrative fees charged		$ 676		$ 1,872
Area Development Agreements
Related Party Transaction [Line Items]
Deferred area development revenue from related parties	260		260		$ 779
Administrative Service | Planet Fitness NAF, LLC
Related Party Transaction [Line Items]
Administrative fees charged	402		1,771
Civil Action Brought By Former Employee | Pending Litigation
Related Party Transaction [Line Items]
Receivables due from related parties	$ 412		$ 412