| Inventories - Finished Goods Available for Resale (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2013 | Dec. 31, 2012 | 
|---|---|---|
| Inventory [Line Items] | ||
| Total | $ 351,201 | $ 339,411 | 
| Weight Management, Targeted Nutrition and Energy, Sports and Fitness [Member] | ||
| Inventory [Line Items] | ||
| Total | 307,200 | 303,800 | 
| Outer Nutrition [Member] | ||
| Inventory [Line Items] | ||
| Total | 15,300 | 17,500 | 
| Literature, Promotional and Other [Member] | ||
| Inventory [Line Items] | ||
| Total | $ 28,700 | $ 18,100 | 
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- 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 
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