Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 118,704	$ 112,329	$ 235,302	$ 219,440
Membership dues
Disaggregation of Revenue [Line Items]
Revenues	89,868	85,549	178,691	167,830
Initiation and processing fees
Disaggregation of Revenue [Line Items]
Revenues	403	332	832	669
Membership revenue
Disaggregation of Revenue [Line Items]
Revenues	90,271	85,881	179,523	168,499
Personal training revenue
Disaggregation of Revenue [Line Items]
Revenues	20,368	19,179	39,857	37,432
Other ancillary club revenue
Disaggregation of Revenue [Line Items]
Revenues	6,388	5,987	12,787	10,791
Ancillary club revenue
Disaggregation of Revenue [Line Items]
Revenues	26,756	25,166	52,644	48,223
Fees and other
Disaggregation of Revenue [Line Items]
Revenues	$ 1,677	$ 1,282	$ 3,135	$ 2,718