New Accounting Pronouncements (Details)	1 Months Ended
Sep. 30, 2011 step
New Accounting Pronouncements
Number of steps involved in the process of impairment test	2

Represents the number of steps involved in the process of impairment test.

No definition available.

Name:	atk_NumberOfStepsInvolvedInProcessOfImpairmentTest
Namespace Prefix:	atk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration