Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Liability payable under tax benefit obligations	$ 55,504		$ 55,504		$ 59,458
Administrative fees charged	3,041	$ 1,136	3,557	$ 1,880
Planet Fitness NAF, LLC
Related Party Transaction [Line Items]
Administrative fees charged		$ 556		$ 1,196
Area Development Agreements
Related Party Transaction [Line Items]
Deferred area development revenue from related parties	299		299		$ 779
Administrative Service | Planet Fitness NAF, LLC
Related Party Transaction [Line Items]
Administrative fees charged	695		1,369
Civil Action Brought By Former Employee | Pending Litigation
Related Party Transaction [Line Items]
Receivables due from related parties	$ 412		$ 412