Share Repurchase Program (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
Share Repurchase Program [Abstract]
Authorized share repurchased program amount	$ 100.0
Amount available under the share repurchase program	$ 82.4

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