Annual report pursuant to Section 13 and 15(d)

REVENUE RECOGNITION - Narrative (Details)

v3.20.1
REVENUE RECOGNITION - Narrative (Details)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2019
USD ($)
Sep. 30, 2019
USD ($)
Jun. 30, 2019
USD ($)
Mar. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2019
USD ($)
product_category
segment
Dec. 31, 2018
USD ($)
Jan. 01, 2018
USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]                      
Retained earnings (accumulated deficit) $ 4,693       $ (2,072)       $ 4,693 $ (2,072)  
Sales 91,695 $ 88,524 $ 90,724 $ 91,272 97,374 $ 88,828 $ 91,266 $ 87,342 362,215 364,810  
Increase in operating income $ 3,908 $ 4,701 $ 4,538 $ 2,978 $ (1,229) $ 3,513 $ 2,186 $ 881 $ 16,125 5,351  
Refund period                 90 days    
Sales returns                 $ 1,900 1,700  
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    
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                 $ 6,200 $ 7,100