Equity - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Jun. 30, 2012
Stockholders Equity Note [Line Items]
Share repurchase program, approved amount	$ 500.0
Share repurchase program, amount remaining for share repurchases	$ 231.0

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