Accounts Receivable and Inventory by Reportable Segments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable
Total accounts receivable	$ 91,078	$ 83,955
Inventories
Total inventories	116,618	104,764
Total segment assets	207,696	188,719
Photonics
Accounts Receivable
Total accounts receivable	31,046	31,536
Inventories
Total inventories	45,227	41,623
Vision
Accounts Receivable
Total accounts receivable	43,941	34,414
Inventories
Total inventories	50,074	42,498
Precision Motion
Accounts Receivable
Total accounts receivable	16,091	18,005
Inventories
Total inventories	$ 21,317	$ 20,643