Debt (Details) (30-Year Variable Rate Gulf Opportunity Zone Bonds [Member], USD $)	Nov. 30, 2010
30-Year Variable Rate Gulf Opportunity Zone Bonds [Member]
Debt instrument face amount	$ 600,000,000
Term of variable rate bonds, years	30

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 21
-Paragraph 16, 20

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