Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 112,329	$ 99,993	$ 219,440	$ 199,073
Membership Dues [Member]
Disaggregation of Revenue [Line Items]
Revenues	85,549	76,421	167,830	151,908
Initiation and Processing Fees [Member]
Disaggregation of Revenue [Line Items]
Revenues	332	596	669	1,582
Total Membership Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	85,881	77,017	168,499	153,490
Personal Training Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	19,179	17,151	37,432	33,669
Other Ancillary Club Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	5,987	4,224	10,791	8,904
Total Ancillary Club Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	25,166	21,375	48,223	42,573
Fees and Other Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 1,282	$ 1,601	$ 2,718	$ 3,010