Description of the credit rating indicative of likelihood of repayment of the debt instrument given by a credit rating agency (for example, Standard and Poor's, Moody's, Fitch).

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 Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_DebtInstrumentCreditRating
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fair Value Measurements and Derivative Instruments (Details 12)	9 Months Ended
	Sep. 30, 2012 Standard & Poor's, BBB- Rating Lower Limit	Sep. 30, 2012 Moody's, Baa3 Rating	Sep. 30, 2012 Standard & Poor's, BB Rating	Sep. 30, 2012 Moody's, Ba1 Rating	Sep. 30, 2012 Maturity of at least five years Lower Limit	Jul. 31, 2012 Maturity in July 2012 item	Sep. 30, 2012 Interest rate contracts item
Derivative instruments disclosure
Credit ratings for senior debt	BBB-	Baa3	BB	Ba1
Number of derivative instruments						1	4
Interest rate instrument term					5 years