Restructuring and Divestiture Charges - Charges Taken Related to Restructuring Actions (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 6 Months Ended 12 Months Ended 3 Months Ended
Mar. 28, 2015
Mar. 29, 2014
Mar. 28, 2015
Mar. 29, 2014
Sep. 27, 2014
Dec. 27, 2014
Dec. 28, 2013
Restructuring Cost and Reserve [Line Items]              
Fiscal restructuring and divestiture charges $ 2.0 $ 11.6 $ 10.0 $ 30.0      
Restructuring | Fiscal 2014 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions         42.2    
Non-cash impairment charge         3.1    
Facility closure costs         0.6    
Other         0.3    
Fiscal restructuring charges         46.2    
Divestiture net charges         5.5    
Fiscal restructuring and divestiture charges         51.7    
Restructuring | Fiscal 2015 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions     9.2        
Facility closure costs     0.8        
Fiscal restructuring charges     10.0        
Restructuring | Consolidation of Diagnostics Operations | Fiscal 2014 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions         2.9    
Non-cash impairment charge         0    
Facility closure costs         0    
Other         0.1    
Fiscal restructuring charges         3.0    
Restructuring | Consolidation of Diagnostics Operations | Fiscal 2015 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions     0.1        
Facility closure costs     0.4        
Fiscal restructuring charges     0.5        
Restructuring | Fiscal 2015 Actions | Fiscal 2014 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions         0    
Non-cash impairment charge         0    
Facility closure costs         0    
Other         0    
Fiscal restructuring charges         0    
Restructuring | Fiscal 2015 Actions | Fiscal 2015 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions     3.0        
Facility closure costs     0        
Fiscal restructuring charges     3.0        
Restructuring | Fiscal 2014 Actions | Fiscal 2014 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions         29.5    
Non-cash impairment charge         0    
Facility closure costs         0    
Other         0    
Fiscal restructuring charges         29.5    
Restructuring | Fiscal 2014 Actions | Fiscal 2015 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions 1.4   5.9     4.5  
Facility closure costs     0.2     0.2  
Fiscal restructuring charges     6.1        
Restructuring | Other Operating Cost Reductions | Fiscal 2014 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions         9.8    
Non-cash impairment charge         3.1   3.1
Facility closure costs         0.6    
Other         0.2    
Fiscal restructuring charges         13.7    
Restructuring | Other Operating Cost Reductions | Fiscal 2015 Charges              
Restructuring Cost and Reserve [Line Items]              
Workforce reductions     0.2        
Facility closure costs     0.2        
Fiscal restructuring charges     $ 0.4