CONSOLIDATED STATEMENTS OF NET INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Income Statement [Abstract]
Service revenues, net	$ 1,081,679	$ 949,121	$ 937,368
Product sales and other, net	225,232	215,781	227,051
Revenues, net	1,306,911	1,164,902	1,164,419
Cost of services	486,293	468,761	477,926
Cost of product sales and other	127,969	110,640	112,406
Cost of revenues	614,262	579,401	590,332
Gross profit	692,649	585,501	574,087
Marketing expenses	200,797	194,398	201,021
Selling, general and administrative expenses	211,224	190,292	205,008
Goodwill impairment	13,323	0	0
Operating income	267,305	200,811	168,058
Interest expense	112,784	115,160	121,843
Other expense, net	472	1,524	2,027
Early extinguishment of debt, net	8,969	0	(11,426)
Income before income taxes	145,080	84,127	55,614
(Benefit from) provision for income taxes	(18,237)	16,634	22,835
Net income	163,317	67,493	32,779
Net loss attributable to the noncontrolling interest	197	206	166
Net income attributable to Weight Watchers International, Inc.	$ 163,514	$ 67,699	$ 32,945
Earnings Per Share attributable to Weight Watchers International, Inc.
Basic	$ 2.54	$ 1.06	$ 0.56
Diluted	$ 2.40	$ 1.03	$ 0.56
Weighted average common shares outstanding
Basic	64,329	63,742	58,369
Diluted	68,248	65,897	58,966