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)

v3.10.0.1
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, 2018
 [1]
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
 [1]
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Revenue from External Customer [Line Items]                      
Total net sales $ 1,186.6 $ 1,242.8 $ 1,285.5 $ 1,176.9 $ 1,093.3 $ 1,085.4 $ 1,146.9 $ 1,102.1 $ 4,891.8 $ 4,427.7 $ 4,488.4
Weight Management [Member]                      
Revenue from External Customer [Line Items]                      
Total net sales                 3,105.8 2,842.5 2,864.5
Targeted Nutrition [Member]                      
Revenue from External Customer [Line Items]                      
Total net sales                 1,243.5 1,082.8 1,062.8
Outer Nutrition [Member]                      
Revenue from External Customer [Line Items]                      
Total net sales                 91.9 93.9 110.4
Literature, Promotional and Other [Member]                      
Revenue from External Customer [Line Items]                      
Total net sales                 142.2 144.7 182.3
Energy, Sports, and Fitness [Member]                      
Revenue from External Customer [Line Items]                      
Total net sales                 $ 308.4 $ 263.8 $ 268.4
[1] The fourth quarters of both 2018 and 2017 include the impact of U.S. Tax Reform enacted during the fourth quarter of 2017, as described further in Note 12, Income Taxes.