Subsequent Events 2012 Share Repurchase Program (Details) (2012 Share Repurchase Program, USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011
2012 Share Repurchase Program
Subsequent Event [Line Items]
Share repurchase program, authorized amount	$ 300.0

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