Annual report pursuant to Section 13 and 15(d)

Revenue - Disaggregated by Product Lines (Details)

v3.20.4
Revenue - Disaggregated by Product Lines (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2020
Sep. 26, 2020
Jun. 27, 2020
Mar. 28, 2020
Dec. 31, 2019
Sep. 28, 2019
Jun. 29, 2019
Mar. 30, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disaggregation of Revenue [Line Items]                      
Sales $ 114,803 $ 106,506 $ 123,694 $ 157,584 $ 198,412 $ 177,018 $ 189,098 $ 208,174 $ 502,587 $ 772,702 $ 803,256
Aerospace                      
Disaggregation of Revenue [Line Items]                      
Sales                 417,988 692,609 675,625
Test Systems                      
Disaggregation of Revenue [Line Items]                      
Sales                 84,599 80,093 127,631
Electrical Power & Motion                      
Disaggregation of Revenue [Line Items]                      
Sales                 179,245 338,237 303,180
Lighting & Safety                      
Disaggregation of Revenue [Line Items]                      
Sales                 118,928 185,462 174,383
Avionics                      
Disaggregation of Revenue [Line Items]                      
Sales                 76,113 106,787 131,849
Systems Certification                      
Disaggregation of Revenue [Line Items]                      
Sales                 6,899 14,401 13,951
Structures                      
Disaggregation of Revenue [Line Items]                      
Sales                 9,832 23,117 24,134
Other                      
Disaggregation of Revenue [Line Items]                      
Sales                 $ 26,971 $ 24,605 $ 28,128