Stockholder's Equity - Additional Information (Detail) - USD ($)								1 Months Ended			12 Months Ended
	Dec. 05, 2016	Nov. 22, 2016	Sep. 28, 2016	Jun. 28, 2016	Aug. 11, 2015	Aug. 05, 2015	Jun. 22, 2015	Nov. 30, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 06, 2015
Class Of Stock [Line Items]
Convertible stock, conversion description											Following the Merger and the Reclassification, the Company and the Continuing LLC Owners entered into an exchange agreement under which the Continuing LLC Owners (or certain permitted transferees thereof) have the right, from time to time and subject to the terms of the exchange agreement, to exchange their Holdings Units, along with a corresponding number of shares of Class B common stock, for shares of Class A common stock (or cash at the option of the Company) on a one-for-one basis, subject to customary conversion rate adjustments for stock splits, stock dividends, reclassifications and similar transactions.
Proceeds from sale of shares											$ 136,000
Common stock dividends declared											169,282,000
Dividend equivalent paid to members of Pla-Fit Holdings											$ 101,729,000	$ 140,000,000	$ 173,900,000
Pla-Fit Holdings, LLC [Member]
Class Of Stock [Line Items]
Number of units held by owners		10,136,285	5,406,019	7,891,160				10,136,285	5,406,019	7,891,160	1,271,146
Continuing LLC Owners [Member]
Class Of Stock [Line Items]
Exchanges of Class B common stock, shares											1,271,146
Continuing LLC Owners [Member] | IPO and Secondary Offering [Member]
Class Of Stock [Line Items]
Percentage of economic interest											37.70%
Number of units held by owners											37,184,925
Class A Common Stock [Member]
Class Of Stock [Line Items]
Number of stock issued during period		15,000,000	8,000,000	11,500,000				15,000,000	8,000,000	11,500,000	1,271,146	10,491,000
Common stock, shares outstanding					36,597,985						61,314,000	36,598,000		0
Share price		$ 23.22	$ 19.62	$ 16.50				$ 23.22	$ 19.62	$ 16.50
Proceeds from sale of shares		$ 0	$ 0	$ 0
Exchanges of Class B common stock, shares											24,705,000
Common stock dividends declared											$ 169,282,000
Common stock dividends paid, per share											$ 2.78
Common stock dividends declared, date											Nov. 10, 2016
Common stock dividends record, date											Nov. 22, 2016
Common stock dividends paid, date											Dec. 05, 2016
Class A Common Stock [Member] | Pla-Fit Holdings, LLC [Member]
Class Of Stock [Line Items]
Reimbursement of IPO expenses												$ 7,697,000
Class A Common Stock [Member] | Pla-Fit Holdings, LLC [Member] | IPO [Member]
Class Of Stock [Line Items]
Number of stock issued during period					15,525,000
Share price					$ 16.00
Class A Common Stock [Member] | Direct TSG Investors [Member]
Class Of Stock [Line Items]
Number of shares converted							26,106,930
Number of stock issued during period		4,863,715	2,593,981	3,608,840	5,033,945			4,863,715	2,593,981	3,608,840
Class A Common Stock [Member] | Direct TSG Investors [Member] | IPO and Secondary Offering [Member]
Class Of Stock [Line Items]
Number of stock issued during period											10,006,450
Percentage of economic interest											10.20%
Percentage of voting power											10.20%
Class A Common Stock [Member] | Continuing LLC Owners [Member]
Class Of Stock [Line Items]
Number of stock issued during period		10,136,285	5,406,019	7,891,160				10,136,285	5,406,019	7,891,160	1,271,146
Number of shares exchanged											24,704,610	10,491,055
Class A Common Stock [Member] | Continuing LLC Owners [Member] | Pla-Fit Holdings, LLC [Member] | IPO [Member]
Class Of Stock [Line Items]
Number of stock issued during period					10,491,055
Aggregate amount of units issued					$ 156,946,000
Class A Common Stock [Member] | Investor | IPO and Secondary Offering [Member]
Class Of Stock [Line Items]
Number of stock issued during period											51,307,348
Percentage of economic interest											52.10%
Percentage of voting power											52.10%
Class B Common Stock [Member]
Class Of Stock [Line Items]
Number of stock issued during period												(10,491,000)
Common stock, shares outstanding											37,185,000	62,112,000		0
Number of shares exchanged											1,271,146
Exchanges of Class B common stock, shares											(24,705,000)
Class B Common Stock [Member] | Continuing LLC Owners [Member]
Class Of Stock [Line Items]
Number of stock issued during period						72,602,810
Common stock dividend and voting rights description											The shares of Class B common stock have no rights to dividends or distributions, whether in cash or stock, but entitle the holder to one vote per share on matters presented to stockholders of the Company.
Number of shares exchanged		10,136,285	5,406,019	7,891,160				10,136,285	5,406,019	7,891,160	1,271,146
Class B Common Stock [Member] | Continuing LLC Owners [Member] | IPO and Secondary Offering [Member]
Class Of Stock [Line Items]
Percentage of voting power											37.70%
Number of units held by owners											37,184,925
Class B Common Stock [Member] | Continuing LLC Owners [Member] | Pla-Fit Holdings, LLC [Member]
Class Of Stock [Line Items]
Number of stock issued during period						72,602,810
Holdings Units [Member]
Class Of Stock [Line Items]
Common stock dividends paid, per share	$ 2.78
Dividend equivalent paid to members of Pla-Fit Holdings	$ 101,729,000
Accrued dividend equivalents for future payments to holders of unvested share awards											$ 3,899,000
Merger Agreement [Member] | Class A Common Stock [Member] | Direct TSG Investors [Member]
Class Of Stock [Line Items]
Number of shares converted							26,106,930