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Debt - Additional Information (Detail) (Revolving Credit Facilities [Member], USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 28, 2012
Sep. 30, 2011
Sep. 28, 2012
Debt Instrument [Line Items]      
Revolving credit facility maturity date   Sep. 30, 2016  
Revolving credit facility maximum borrowing availability   $ 150.0  
Revolving credit facility interest date Borrowings under the revolving credit facility bear a variable interest rate equal to (i) the greater of the lender's prime rate, the federal funds effective rate plus 0.5%, or an adjusted LIBOR plus 1.0%, in each case plus either an additional 1.25%, 1.50% or 1.75%, subject to certain conditions, or (ii) an adjusted LIBOR rate plus either 2.25%, 2.50% or 2.75%, subject to certain conditions.    
Revolving credit facility, LIBOR rate Adjusted LIBOR plus 1.0%    
Revolving credit facility federal funds effective rate Federal funds effective rate plus 0.5%    
Federal funds effective rate 0.50%    
LIBOR rate 1.00%    
Outstanding borrowing under revolving credit facility $ 0   $ 0
Interest Rate LIBOR One [Member]
     
Debt Instrument [Line Items]      
Adjusted LIBOR rate percentage 1.25%    
Interest Rate LIBOR Two [Member]
     
Debt Instrument [Line Items]      
Adjusted LIBOR rate percentage 1.50%    
Interest Rate LIBOR Three [Member]
     
Debt Instrument [Line Items]      
Adjusted LIBOR rate percentage 1.75%    
Interest Rate LIBOR Four [Member]
     
Debt Instrument [Line Items]      
Adjusted LIBOR rate percentage 2.25%    
Interest Rate LIBOR Five [Member]
     
Debt Instrument [Line Items]      
Adjusted LIBOR rate percentage 2.50%    
Interest Rate LIBOR Six [Member]
     
Debt Instrument [Line Items]      
Adjusted LIBOR rate percentage 2.75%