Acquisition of Controlling Interest in Equity Method Investment (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Mar. 31, 2011	Jun. 30, 2011	Jun. 30, 2010
Equity Method Investments [Abstract]
Remeasurement gain, equity interest in acquiree	$ 123.4	$ 123.4	$ 0

In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)(2)
-URI http://asc.fasb.org/extlink&oid=6909870&loc=d3e1392-128463

Name:	us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementGain
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration