CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands		12 Months Ended
		Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 163,317	$ 67,493	$ 32,779
Other comprehensive gain (loss):
Foreign currency translation gain (loss)		9,848	5,556	(27,824)
Income tax (expense) benefit on foreign currency translation gain (loss)		(3,840)	(2,089)	10,851
Foreign currency translation gain (loss), net of taxes		6,008	3,467	(16,973)
Gain (loss) on derivatives		17,393	11,821	(2,096)
Income tax (expense) benefit on gain (loss) on derivatives		(6,783)	(4,688)	817
Gain (loss) on derivatives, net of taxes		10,610	7,133	(1,279)
Total other comprehensive gain (loss)	[1]	16,618	10,600	(18,252)
Comprehensive income		179,935	78,093	14,527
Net loss attributable to the noncontrolling interest		197	206	166
Foreign currency translation loss (gain), net of taxes attributable to the noncontrolling interest		35	(455)	937
Comprehensive loss (income) attributable to the noncontrolling interest		232	(249)	1,103
Comprehensive income attributable to Weight Watchers International, Inc.		$ 180,167	$ 77,844	$ 15,630

[1] Amounts in parentheses indicate debits