Dividends (Details) (USD $)	0 Months Ended
Nov. 11, 2014	Aug. 19, 2014	May 28, 2014	Feb. 24, 2014	Nov. 12, 2013	Aug. 27, 2013	May 23, 2013	Feb. 26, 2013
Dividends
Dividend per share (usd per share)	$ 0.54	$ 0.54	$ 0.54	$ 0.54	$ 0.54	$ 0.54	$ 0.54	$ 0.54
Total amount declared	$ 307,000,000us-gaap_DividendsCommonStock	$ 308,000,000us-gaap_DividendsCommonStock	$ 307,000,000us-gaap_DividendsCommonStock	$ 309,000,000us-gaap_DividendsCommonStock	$ 320,536,173.38us-gaap_DividendsCommonStock	$ 321,000,000us-gaap_DividendsCommonStock	$ 320,000,000us-gaap_DividendsCommonStock	$ 339,000,000us-gaap_DividendsCommonStock

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