Gain on Acquisition of Controlling Interest in Equity Investment (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	3 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013 Other Income (Expense) [Member] Changes Measurement [Member]
Business Acquisition [Line Items]
Pre-tax gain on remeasurement of existing equity interest	$ 30	$ 0	$ 30

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=7659399&loc=d3e1392-128463

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