Segment and Geographic Data - Information About Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 03, 2021	Dec. 31, 2022	Jan. 01, 2022	Jan. 02, 2021
Segment Reporting Information [Line Items]
Revenues, net		$ 1,040,856	$ 1,212,463	$ 1,378,124
Operating (loss) income		(282,950)	196,284	216,162
Interest expense		81,141	87,909	123,310
Other expense, net		1,691	1,358	349
Early extinguishment of debt	$ 29,169		30,352
(Benefit from) provision for income taxes		(114,379)	9,773	17,462
Net (loss) income		(251,403)	66,892	75,041
Net loss attributable to the noncontrolling interest				38
Net (loss) income attributable to WW International, Inc.		(251,403)	66,892	75,079
Depreciation and amortization		48,819	54,686	59,522
Operating Segments
Segment Reporting Information [Line Items]
Operating (loss) income		(135,667)	348,879	407,460
Depreciation and amortization		34,181	41,941	42,742
General Corporate
Segment Reporting Information [Line Items]
General corporate expenses		147,283	152,595	191,298
Depreciation and amortization		14,638	12,745	16,780
North America
Segment Reporting Information [Line Items]
Revenues, net		726,884	814,797	942,100
North America | Operating Segments
Segment Reporting Information [Line Items]
Revenues, net		726,884	814,797	942,100
Operating (loss) income		(219,875)	217,901	269,580
Depreciation and amortization		32,521	39,270	39,740
Continental Europe
Segment Reporting Information [Line Items]
Revenues, net		239,129	297,910	313,380
Continental Europe | Operating Segments
Segment Reporting Information [Line Items]
Revenues, net		239,129	297,910	313,380
Operating (loss) income		91,599	117,390	124,891
Depreciation and amortization		763	1,468	1,615
United Kingdom
Segment Reporting Information [Line Items]
Revenues, net		47,995	65,820	84,387
United Kingdom | Operating Segments
Segment Reporting Information [Line Items]
Revenues, net		47,995	65,820	84,387
Operating (loss) income		(7,457)	8,134	10,648
Depreciation and amortization		627	799	1,017
Other
Segment Reporting Information [Line Items]
Revenues, net		26,848	33,936	38,257
Other | Operating Segments
Segment Reporting Information [Line Items]
Revenues, net		26,848	33,936	38,257
Operating (loss) income		66	5,454	2,341
Depreciation and amortization		$ 270	$ 404	$ 370