Long-term Debt (Narrative) (Details) (USD $) In Billions, unless otherwise specified	3 Months Ended
Apr. 30, 2011
Long-term Debt
Aggregate net proceeds from note issuance	$ 4.9
Date of first repayment of long-term debt	October 15, 2011
Repayment of debt, percentage of principal amount under normal conditions	100.00%

Date that the debt agreement requires the first payment to be made, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

Name:	us-gaap_DebtInstrumentDateOfFirstRequiredPayment
Namespace Prefix:	us-gaap
Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	duration