Annual report pursuant to Section 13 and 15(d)

REVENUE RECOGNITION - Narrative (Details)

v3.10.0.1
REVENUE RECOGNITION - Narrative (Details)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2018
USD ($)
segment
product_category
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Jan. 01, 2018
USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]                        
Retained earnings (accumulated deficit) $ (2,072)       $ (2,072)       $ (2,072) $ (2,072)    
Sales 97,374 $ 88,828 $ 91,266 $ 87,342 88,286 $ 89,301 $ 81,344 $ 83,098 364,810 342,029 $ 341,159  
Increase in operating income $ (1,229) $ 3,513 $ 2,186 $ 881 $ (2,841) $ 2,154 $ 23 $ 2,051 $ 5,351 1,387 10,039  
Refund period                 90 days      
Sales returns                 $ 1,700 1,600 1,400  
Number of principal categories of products | product_category                 6      
Number of business segments | segment                 4      
NSP Americas; NSP Russia, Central and Eastern Europe; and NSP China                        
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]                        
Number of operating segments | segment                 3      
Synergy WorldWide                        
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]                        
Sales                 $ 141,028 123,833 124,793  
Number of operating segments | segment                 1      
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606                        
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]                        
Retained earnings (accumulated deficit)                       $ 900
Sales                 $ 200      
Increase in operating income                 47      
Shipping and Handling                        
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]                        
Sales                 $ 7,100 $ 8,200 $ 9,200