Document and Entity Information - shares
3 Months Ended
Dec. 30, 2016
Feb. 07, 2017
Document and Entity Information [Abstract]    
Entity Registrant Name CPI International Holding Corp.  
Entity Central Index Key 0001515003  
Current Fiscal Year End Date --09-29  
Entity Filer Category Non-accelerated Filer  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q1  
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Dec. 30, 2016  
Entity Common Stock, Shares Outstanding   1,110