Franchise Rights Acquired, Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 30, 2017	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Goodwill and Intangible Assets Disclosure
Goodwill impairment		$ 13,323	$ 0	$ 0
Gross Carrying Amount	$ 221,263	221,263	195,438
Accumulated Amortization	174,727	174,727	136,826
Finite-lived intangible assets, aggregate amortization expense		36,040	35,752	$ 34,719
Capitalized software costs
Goodwill and Intangible Assets Disclosure
Gross Carrying Amount	111,617	111,617	103,362
Accumulated Amortization	94,697	94,697	77,941
Website development costs
Goodwill and Intangible Assets Disclosure
Gross Carrying Amount	90,096	90,096	72,778
Accumulated Amortization	61,125	61,125	40,543
Other
Goodwill and Intangible Assets Disclosure
Gross Carrying Amount	3,793	3,793	3,655
Accumulated Amortization	3,546	3,546	3,144
Franchise Rights
Goodwill and Intangible Assets Disclosure
Gross Carrying Amount	4,526	4,526	4,551
Accumulated Amortization	4,526	$ 4,526	4,551
Franchise Rights | VPM
Goodwill and Intangible Assets Disclosure
Amortization period		2 years
Franchise Rights | Weight Watchers of Greater Miami, Inc.
Goodwill and Intangible Assets Disclosure
Amortization period		3 months
Adjustments | Capitalized software costs
Goodwill and Intangible Assets Disclosure
Gross Carrying Amount			(23,375)
Accumulated Amortization			(23,375)
Adjustments | Website development costs
Goodwill and Intangible Assets Disclosure
Gross Carrying Amount			(47,193)
Accumulated Amortization			(47,193)
Adjustments | Other
Goodwill and Intangible Assets Disclosure
Gross Carrying Amount			(4,290)
Accumulated Amortization			(4,290)
BRAZIL
Goodwill and Intangible Assets Disclosure
Goodwill impairment	$ 13,323	$ 13,323	$ 0