Derivative Financial Instruments Derivative Financial Instruments - Cash Flow Interest Rate Risk (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 InterestRateSwap	Dec. 31, 2011 InterestRateSwap
Interest Rate Swap
Derivative [Line Items]
Number of Interest Rate Derivatives Held	2	2
Notional amount of interest rate derivatives	$ 26	$ 26
Interest rate cap
Derivative [Line Items]
Number of Interest Rate Derivatives Held	1	1
Notional amount of interest rate derivatives	$ 13	$ 13

Aggregate notional amount of all interest rate derivatives designated as hedging instruments in cash flow hedges. Notional amount refers to the monetary amount specified in the interest rate derivative contract.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

Name:	us-gaap_NotionalAmountOfInterestRateCashFlowHedgeDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant