Dividends (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended
Aug. 27, 2013	May 23, 2013	Feb. 26, 2013	Nov. 13, 2012	May 24, 2012	Feb. 12, 2012	Nov. 15, 2011	Aug. 23, 2011
Dividends
Dividend Per Share (usd per share)	$ 0.54	$ 0.54	$ 0.54	$ 0.54	$ 0.725	$ 0.725	$ 0.725	$ 0.725
Total amount declared	$ 321	$ 320	$ 339	$ 321	$ 453	$ 452	$ 454	$ 452

Amount of paid and unpaid common stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 405

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

Name:	us-gaap_DividendsCommonStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration