Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation - Additional Information (Detail)

v3.8.0.1
Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2017
Sep. 24, 2016
Sep. 26, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granting of options 639,000    
Selling, General and Administrative Expenses      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense $ 11.1 $ 8.4 $ 8.3
Restricted Stock Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares of restricted stock 196,000    
Restricted Stock Awards | Selling, General and Administrative Expenses      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense $ 5.8 4.5 3.1
Stock Options | Selling, General and Administrative Expenses      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense 2.9 2.2 3.3
401 (K) | Selling, General and Administrative Expenses      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense $ 2.4 $ 1.7 $ 1.9
2003 Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share based compensation, number of shares 5,800,000    
2003 Plan | Preferred Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share based compensation, number of shares 500,000    
Shares reserved for outstanding equity awards 0    
Shares reserved for future awards 500,000    
2003 Plan | Class A common stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share based compensation, number of shares 19,734,982    
Shares reserved for outstanding equity awards 3,600,000    
Shares reserved for future awards 11,700,000    
2003 Plan | Common stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares reserved for outstanding equity awards 32,100    
Shares reserved for future awards 4,600,000    
Director Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granting of options 200,000    
Director Plan | Restricted Stock Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares of restricted stock 20,000