This item represents the amount of the total change in unrealized (holding) gains or losses for the period which are included in the statement of income (or changes in net assets) in other income. Such unrealized (holding) gains or losses relate to those energy commodity contracts still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

Name:	kmp_FairValueAssetsLiabilitiesNetMeasuredOnRecurringBasisChangeInUnrealizedGainLossIncludedInOtherIncome
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents energy commodity derivative contract assets, measured at fair value on a recurring basis.

+ Details

Name:	kmp_FairValueAssetsMeasuredOnRecurringBasisEnergyCommodityDerivativeContractsAssets
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents interest rate swap agreements assets, measured at fair value on a recurring basis.

+ Details

Name:	kmp_FairValueAssetsMeasuredOnRecurringBasisInterestRateSwapAgreementsAssets
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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- Details

Name:	kmp_FairValueByBalanceSheetGroupingLineItems
Namespace Prefix:	kmp
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents energy commodity derivative contract liabilities, measured at fair value on a recurring basis.

+ Details

Name:	kmp_FairValueLiabilitiesMeasuredOnRecurringBasisEnergyCommodityDerivativeContractsLiabilities
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents interest rate swap agreements liabilities, measured at fair value on a recurring basis.

+ Details

Name:	kmp_FairValueLiabilitiesMeasuredOnRecurringBasisInterestRateSwapAgreementsLiabilities
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	kmp_FairValueLiabilitiesMeasuredOnRecurringBasisLineItems
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- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets or liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

+ Details

Name:	kmp_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetLiabilityGainLossIncludedInEarnings
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets or liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in other comprehensive income (a separate component of shareholders' equity).

+ Details

Name:	kmp_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetLiabilityGainLossIncludedInOtherComprehensiveIncome
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents an asset and liability measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Purchases that have taken place during the period in relation to assets or liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ Details

Name:	kmp_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetLiabilityPurchases
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Settlements that have taken place during the period in relation to assets or liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ Details

Name:	kmp_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetLiabilitySettlements
Namespace Prefix:	kmp
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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Period Type:	duration

- Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DerivativeGainLossOnDerivativeNetAbstract
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Data Type:	xbrli:stringItemType
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Period Type:	duration

Fair Value (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
Fair Value (Details) (USD $) In Millions	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Fair Value, Assets Measured on Recurring Basis [Line Items]
Energy commodity derivative contracts	$ 61.3		$ 61.3		$ 67.1
Interest rate swap agreements	270.8		270.8		217.6
Fair Value, Liabilities Measured on Recurring Basis [Line Items]
Energy commodity derivative contracts	335.5		335.5		384.5
Interest rate swap agreements	58.1		58.1		69.2
Significant unobservable inputs (Level 3)
Beginning of period	(3.2)	22.6	18.8	13.0
Total gains or (losses) [Abstract]
Included in earnings	2.7	11.1	2.8	11.1
Included in other comprehensive income	7.3	7.0	(15.5)	15.6
Purchases	0	0	4.6	0
Settlements	(0.1)	5.9	(4.0)	6.9
End of period	6.7	46.6	6.7	46.6
The amount of total gains or (losses) for the period included in earnings attributable to the change in unrealized gains or (losses) relating to assets held at the reporting date	(3.7)	8.9	1.0	10.1
Quoted prices in active markets for identical assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis [Line Items]
Energy commodity derivative contracts	13.5		13.5
Quoted prices in active markets for identical assets (Level 1) [Member]
Fair Value, Liabilities Measured on Recurring Basis [Line Items]
Energy commodity derivative contracts	2.5		2.5
Significant other observable inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis [Line Items]
Energy commodity derivative contracts	15.2		15.2		23.5
Interest rate swap agreements	270.8		270.8		217.6
Significant other observable inputs (Level 2) [Member]
Fair Value, Liabilities Measured on Recurring Basis [Line Items]
Energy commodity derivative contracts	307.1		307.1		359.7
Interest rate swap agreements	58.1		58.1		69.2
Significant unobservable inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis [Line Items]
Energy commodity derivative contracts	32.6		32.6		43.6
Significant unobservable inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis [Line Items]
Energy commodity derivative contracts	25.9		25.9		24.8
Carrying Value [Member]
Fair Value, by Balance Sheet Grouping [Line Items]
Total debt	11,406.9		11,406.9		11,539.8
Estimated Fair Value [Member]
Fair Value, by Balance Sheet Grouping [Line Items]
Total debt	$ 12,389.9		$ 12,389.9		$ 12,443.4