Summary of Significant Accounting Policies (as Restated) - Summary of Effect of Correction to Applicable Reporting Periods for Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Mar. 20, 2019	[1]	Mar. 19, 2019	Dec. 31, 2018	Dec. 31, 2017
Warrant liabilities	$ 104,700				$ 55,900
Total liabilities	381,451	$ 338,816	$ 319,419	$ 299,482	333,201	$ 316,517	$ 329,727	$ 330,535
Additional paid-in capital	649,540	634,722	633,612	607,289	616,888	619,135	619,010	619,010
Accumulated deficit	(323,246)	(250,485)	(202,938)	(183,631)	(35,269)	(27,412)	(30,374)	(30,383)
Total OneSpaWorld shareholders' equity	320,828	378,459	424,414	417,897	582,344	591,398	588,251	588,372
Total shareholders' equity	320,828	378,459	424,414	417,897	590,468	599,384	594,929	594,100	$ 633,590		$ 199,006	$ (127,583)	$ 225,281
As Reported [Member]
Total liabilities	276,751	277,516	283,219	293,882	277,301	269,617	282,227	286,635
Additional paid-in capital	727,054	713,622	712,512	643,489	653,088	655,335	655,210	655,210
Accumulated deficit	(296,060)	(268,085)	(245,638)	(214,231)	(15,569)	(16,712)	(19,074)	(22,683)
Total OneSpaWorld shareholders' equity		439,759	460,614	423,497	638,244	638,298	635,751	632,272
Total shareholders' equity	425,528	439,759	460,614	423,497	646,368	646,284	642,429	638,000
Restatement Impact [Member]
Warrant liabilities	104,700				55,900
Total liabilities	104,700	61,300	36,200	5,600	55,900	46,900	47,500	43,900
Additional paid-in capital	(77,514)	(78,900)	(78,900)	(36,200)	(36,200)	(36,200)	(36,200)	(36,200)
Accumulated deficit	(27,186)	17,600	42,700	30,600	(19,700)	(10,700)	(11,300)	(7,700)
Total OneSpaWorld shareholders' equity		(61,300)	(36,200)	(5,600)	(55,900)	(46,900)	(47,500)	(43,900)
Total shareholders' equity	$ (104,700)	$ (61,300)	$ (36,200)	$ (5,600)	$ (55,900)	$ (46,900)	$ (47,500)	$ (43,900)

[1] Initial equity balances of the Successor reflect the equity of the accounting acquirer, Haymaker Acquisition Corp., and the issuance of common stock, warrants and cash contributed by Haymaker in connection with the acquisition of OSW Predecessor.