Consolidated Statements of Cash Flows (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements of Cash Flows [Abstract]
Net of cash received from interest rate swaps	$ 24	$ 24	$ 6

The net cash outflow or inflow from derivative instruments during the period, which are classified as financing activities, excluding those designated as hedging instruments.

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

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 23

-Name Accounting Standards Codification

-Publisher FASB

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3505-108585

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