Acquisitions and Dispositions (Acquisitions - Narrative) (Details) (Pending Acquisition of Administradora de Fondos de Pensiones Provida S.A. [Member], USD $) In Billions, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Business Acquisition [Line Items]
Business Acquisition, Name of Acquired Entity	Administradora de Fondos de Pensiones Provida S.A. (“Provida”)
Pending Business Acquisition, Percentage of Voting Interests To Be Acquired Directly From Seller	64.30%
Maximum [Member]
Business Acquisition [Line Items]
Pending Business Acquisition, Anticipated Approximate Cost of Acquired Entity, Purchase Price	2

Name of the acquired entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7659399&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionNameOfAcquiredEntity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration