Annual report pursuant to Section 13 and 15(d)

Segment Information - Schedule of Entity-Wide Information, Revenue from External Customers by Products and Services (Detail)

v3.8.0.1
Segment Information - Schedule of Entity-Wide Information, Revenue from External Customers by Products and Services (Detail) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2017
 [1]
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
 [1]
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Revenue from External Customer [Line Items]                      
Total Net Sales $ 1,093.3 $ 1,085.4 $ 1,146.9 $ 1,102.1 $ 1,045.0 $ 1,122.0 $ 1,201.8 $ 1,119.6 $ 4,427.7 $ 4,488.4 $ 4,469.0
Weight Management [Member]                      
Revenue from External Customer [Line Items]                      
Total Net Sales                 2,842.5 2,864.5 2,862.8
Targeted Nutrition [Member]                      
Revenue from External Customer [Line Items]                      
Total Net Sales                 1,082.8 1,062.8 1,015.4
Energy, Sports & Fitness [Member]                      
Revenue from External Customer [Line Items]                      
Total Net Sales                 263.8 268.4 250.9
Outer Nutrition [Member]                      
Revenue from External Customer [Line Items]                      
Total Net Sales                 93.9 110.4 133.0
Literature, Promotional and Other [Member]                      
Revenue from External Customer [Line Items]                      
Total Net Sales                 $ 144.7 $ 182.3 $ 206.9
[1] Includes the impact of the U.S. Tax Reform enacted during the fourth quarter of 2017, as described further in Note 12, Income Taxes.