Interest rate stated in the contractual debt agreement.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Supplemental Guarantor Information (Details)	9 Months Ended
Supplemental Guarantor Information (Details)	Sep. 30, 2012	Sep. 30, 2012 5.4 percent senior notes due January 2015	Dec. 31, 2011 5.4 percent senior notes due January 2015	Sep. 30, 2012 8.4 percent senior notes due May 2017	Dec. 31, 2011 8.4 percent senior notes due May 2017	Sep. 30, 2012 1.6 percent convertible senior notes due May 2018	Dec. 31, 2011 1.6 percent convertible senior notes due May 2018	Sep. 30, 2012 6.6 percent senior notes due May 2020	Dec. 31, 2011 6.6 percent senior notes due May 2020	Sep. 30, 2012 5.4 percent senior notes due October 2022
Supplemental Guarantor Information
Percentage ownership of Guarantor Subsidiaries	100.00%
Interest rate on obligations of the parent, guaranteed by the Guarantor Subsidiaries
Interest rate stated percentage		5.40%	5.40%	8.40%	8.40%	1.60%	1.60%	6.60%	6.60%	5.40%