Annual report pursuant to Section 13 and 15(d)

Industry, Segment and Geographic Information - Sales and Assets (Details)

v3.8.0.1
Industry, Segment and Geographic Information - Sales and Assets (Details)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
USD ($)
country
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
country
Sep. 30, 2016
USD ($)
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Dec. 31, 2017
USD ($)
country
Dec. 31, 2016
USD ($)
country
Dec. 31, 2015
USD ($)
country
Net sales to unaffiliated customers and identifiable assets by geographic areas                      
Number of countries other than USA that make up 10% or more of net sales | country 0       0       0 0 0
Net sales to Unaffiliated Customers $ 126,956 $ 106,646 $ 102,982 $ 112,795 $ 119,965 $ 99,586 $ 105,257 $ 93,323 $ 449,379 $ 418,131 $ 382,090
Identifiable Assets by Geographic Areas 102,725       113,698       102,725 113,698 94,082
USA                      
Net sales to unaffiliated customers and identifiable assets by geographic areas                      
Net sales to Unaffiliated Customers                 389,925 364,989 336,110
Identifiable Assets by Geographic Areas 95,516       106,014       95,516 106,014 87,679
Canada                      
Net sales to unaffiliated customers and identifiable assets by geographic areas                      
Net sales to Unaffiliated Customers                 30,289 28,491 23,957
Identifiable Assets by Geographic Areas $ 7,209       $ 7,684       7,209 7,684 6,403
Rest of the world                      
Net sales to unaffiliated customers and identifiable assets by geographic areas                      
Net sales to Unaffiliated Customers                 $ 29,165 $ 24,651 $ 22,023