Stockholders' Equity - Additional Information (Detail) (USD $)	35 Months Ended
Jul. 31, 2011
Stockholders Equity Note [Abstract]
Share-repurchase program amount	$ 5,000,000,000

The amount authorized by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration