Commitments, Contingencies and Other Items - Other Commitments (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Amount outstanding under letters of credit or other similar obligations	$ 27	$ 31
Collateralized by cash, that is reflected on the consolidated balance sheets as restricted cash	$ 25	$ 29

The value of the collateral (typically cash) that the entity receives in a financing transaction in exchange for securities lent. This item represents a liability in the financial statements of the lender of the securities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(ii))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 25

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=7523047&loc=d3e113275-111724

Name:	us-gaap_CollateralizedFinancings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant