Stockholders' Equity - Additional Information (Detail) (USD $) In Billions, unless otherwise specified	1 Months Ended	9 Months Ended
Sep. 22, 2008	Mar. 31, 2012
Share Repurchases [Line Items]
Unused amount of share repurchase program		$ 9.2
Amount available for repurchase under the current share repurchase program approved by the company's Board of Directors	$ 40.0
Expiration date of the share repurchase program		Sep. 30, 2013

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

No definition available.

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