Total monetary amount specified by the derivative(s). Expressed as an absolute value.

No definition available.

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

+ Details

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

- Definition

Estimated fair value of the debt instrument at the balance-sheet date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

+ Details

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

- Details

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the hedged item as of the balance sheet date related to the derivative. For example, the hedged balance on a debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAmountOfHedgedItem
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The average percentage points added to the reference rate to compute the variable rate on the group of interest rate derivatives.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAverageBasisSpreadOnVariableRate
Namespace Prefix:	us-gaap_
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of the hedged item related to the derivative. Includes the type of instrument hedged, contract amount, term, and so forth.

+ References

No definition available.

+ Details

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

- Definition

The hedge designation, if any, elected for the derivative.

+ References

No definition available.

+ Details

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

- Definition

Description of the type of derivative instrument, such as a swap, forward, and option. Excludes the underlying risk of the instrument.

+ References

No definition available.

+ Details

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

- Definition

Description of the primary underlying risk exposure associated with the derivative. For example, interest rate risk, credit risk, foreign exchange rate risk, or overall price risk.

+ References

No definition available.

+ Details

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

- Details

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

- Definition

Fair value as of the balance sheet date of all derivative assets designated as interest rate fair value hedging instruments.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 17

+ Details

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

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents notes payable as of the balance sheet date.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

+ Details

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

Fair Value (Details) (USD $)	12 Months Ended			12 Months Ended
Fair Value (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2011 Fair Value Inputs - Level 2 [Member]	Dec. 31, 2010 Fair Value Inputs - Level 2 [Member]	Dec. 31, 2011 Senior Notes due 2013 [Member]	Dec. 31, 2011 Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Face Value of Debt Instrument				$ 500,000,000	$ 500,000,000
Maturity Date				Aug. 15, 2013	Sep. 15, 2019
Fair Value of Debt Instrument				540,000,000	583,000,000
Short-term debt	67,000,000
Underlying risk	interest rate
Notional amount	500,000,000
Type of instrument	interest rate swap agreements
Hedge designation	fair value hedges
Amount of hedged item	500,000,000
Description of hedged item	senior notes due 2013
Basis spread on Variable rate	4.377%
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Interest Rate Fair Value Hedge Asset		$ 11,600,000	$ 14,100,000