COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Dec. 31, 2017 USD ($)
Firm Transportation and Storage Contracts [Abstract]
2018	$ 46.1
2019	37.6
2020	37.3
2021	23.0
2022	14.2
Thereafter	20.8
Total	$ 179.0

No definition available.

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- Definition

The remaining amount of the fixed and determinable portion of an unrecorded firm transportation and storage contract purchase obligation to be paid after five years from the balance sheet date.

+ References

No definition available.

+ Details

Name:	oke_UnrecordedPurchaseObligationDueAfterFiveYears
Namespace Prefix:	oke_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded firm transportation and storage contract purchase obligation to be paid within one year of the balance sheet date.

+ References

No definition available.

+ Details

Name:	oke_UnrecordedPurchaseObligationDueCurrent
Namespace Prefix:	oke_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded firm transportation and storage contract purchase obligation to be paid in more than three and within four years from the balance sheet date.

+ References

No definition available.

+ Details

Name:	oke_UnrecordedPurchaseObligationDueInFourYears
Namespace Prefix:	oke_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded firm transportation and storage contract purchase obligation to be paid in more than two and within three years from the balance sheet date.

+ References

No definition available.

+ Details

Name:	oke_UnrecordedPurchaseObligationDueInThreeYears
Namespace Prefix:	oke_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded firm transportation and storage contract purchase obligation to be paid in more than one and within two years from the balance sheet date.

+ References

No definition available.

+ Details

Name:	oke_UnrecordedPurchaseObligationDueInTwoYears
Namespace Prefix:	oke_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of the fixed and determinable portion of an unrecorded firm transportation and storage contract purchase obligation as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	oke_UnrecordedPurchaseObligationTotal
Namespace Prefix:	oke_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded firm transportation and storage contract purchase obligation to be paid in more than four and within five years from the balance sheet date.

+ References

No definition available.

+ Details

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Namespace Prefix:	oke_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant