Lines of Credit (Details) (USD $) In Millions, unless otherwise specified	Aug. 27, 2011 loc
Lines of credit and letters of credit disclosures
Number of uncommitted lines of credit maintained	2
Uncommitted line of credit - expiration date of February 29, 2012
Lines of credit and letters of credit disclosures
Uncommitted line of credit maintained	$ 100
Uncommitted line of credit - expiration date of September 2, 2011
Lines of credit and letters of credit disclosures
Uncommitted line of credit maintained	$ 100

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant