Revenue - Additional Information (Details) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($) jurisdiction session	Dec. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Average member life		20 months	26 months
Deferred revenue	$ 40,195	$ 40,195	$ 37,459
Deferred revenue recognized	5,897	$ 18,521
Minimum
Disaggregation of Revenue [Line Items]
Number of personal training sessions per month | session		4
Maximum
Disaggregation of Revenue [Line Items]
Number of personal training sessions per month | session		12
Initiation and processing fees
Disaggregation of Revenue [Line Items]
Deferred revenue, amortization period		12 months
Personal training revenue
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 12,500	$ 12,500	$ 12,500
Number of jurisdictions in which expired sessions are not escheatable | jurisdiction		6