Inventories - Finished Goods Available for Resale (Detail) - USD ($) $ in Millions  | 
Dec. 31, 2015  | 
Dec. 31, 2014  | 
|---|---|---|
| Inventory [Line Items] | ||
| Total | $ 332.0 | $ 377.7 | 
| Weight Management, Targeted Nutrition and Energy, Sports and Fitness [Member] | ||
| Inventory [Line Items] | ||
| Total | 304.3 | 340.5 | 
| Outer Nutrition [Member] | ||
| Inventory [Line Items] | ||
| Total | 13.5 | 20.2 | 
| Literature, Promotional and Other [Member] | ||
| Inventory [Line Items] | ||
| Total | $ 14.2 | $ 17.0 | 
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
  | 
| X | ||||||||||
- Definition Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
| X | ||||||||||
- Details 
  | 
| X | ||||||||||
- Details 
  | 
| X | ||||||||||
- Details 
  |