Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Jan. 01, 2022	Jan. 02, 2021	Dec. 28, 2019
Numerator:
Net income attributable to WW International, Inc.	$ 66,892	$ 75,079	$ 119,616
Denominator:
Weighted average shares of common stock outstanding	69,640	67,849	67,188
Effect of dilutive common stock equivalents	1,104	2,171	2,362
Weighted average diluted common shares outstanding	70,744	70,020	69,550
Earnings per share attributable to WW International, Inc.
Basic	$ 0.96	$ 1.11	$ 1.78
Diluted	$ 0.95	$ 1.07	$ 1.72