Information About Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 04, 2015	Jun. 28, 2014	Jul. 04, 2015	Jun. 28, 2014
Segment Reporting Information [Line Items]
Net revenue	$ 309,754	$ 397,547	$ 631,857	$ 806,905
Segment operating income	70,580	114,564	88,624	165,617
Interest expense	30,460	31,191	61,564	56,453
Other expense, net	344	889	919	1,159
Early extinguishment of debt	(6,700)	0	(11,476)	0
Gain on Brazil acquisition	0	0	0	(10,540)
Provision for taxes	18,696	28,392	15,321	42,922
Net income	27,780	54,092	22,296	75,623
Less: Net loss (income) attributable to the noncontrolling interest	97	(90)	148	(90)
Net income attributable to Weight Watchers International, Inc.	27,877	54,002	22,444	75,533
Depreciation and amortization	16,099	14,109	31,854	27,522
Operating Segments
Segment Reporting Information [Line Items]
Segment operating income	84,532	140,030	120,288	203,223
Depreciation and amortization	12,897	10,075	25,428	19,352
General corporate expenses
Segment Reporting Information [Line Items]
General corporate expenses	(13,952)	(25,466)	(31,664)	(37,606)
Depreciation and amortization	3,202	4,034	6,426	8,170
North America
Segment Reporting Information [Line Items]
Net revenue	200,772	248,490	406,328	512,896
North America | Operating Segments
Segment Reporting Information [Line Items]
Segment operating income	51,000	88,865	69,020	146,673
Depreciation and amortization	11,866	8,358	23,341	16,336
United Kingdom
Segment Reporting Information [Line Items]
Net revenue	32,785	43,428	67,155	85,627
United Kingdom | Operating Segments
Segment Reporting Information [Line Items]
Segment operating income	8,268	13,397	14,449	11,851
Depreciation and amortization	195	356	382	714
Continental Europe
Segment Reporting Information [Line Items]
Net revenue	62,206	84,250	128,949	168,481
Continental Europe | Operating Segments
Segment Reporting Information [Line Items]
Segment operating income	22,582	32,075	32,639	37,918
Depreciation and amortization	476	616	961	1,209
Other
Segment Reporting Information [Line Items]
Net revenue	13,991	21,379	29,425	39,901
Other | Operating Segments
Segment Reporting Information [Line Items]
Segment operating income	2,682	5,693	4,180	6,781
Depreciation and amortization	$ 360	$ 745	$ 744	$ 1,093