Number of customers the natural gas distribution service segment services.

No definition available.

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- Definition

Amount recorded as a deferred tax asset related to the adoption of ASU 2016-09, which represents an operating loss carryforward tax benefit available to reduce future taxable income.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Line items for Significant accounting policies of the reporting entity.

+ References

No definition available.

+ Details

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Namespace Prefix:	ogs_
Data Type:	xbrli:stringItemType
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Period Type:	duration

- Definition

The amount of a reclassification adjustment made to prior period financial statement amounts.

+ References

No definition available.

+ Details

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

- Definition

The aggregate cash inflow comprised of the amount received from (a) employees to acquire the entity's shares under incentive awards, including stock option exercises and restricted stock arrangements, and (b) the excess tax benefit arising from such transactions.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Disclosure of the extent of enterprise reliance on its major customers. For example, includes revenues from transactions with a single external customer amounting to 10 percent or more of the entity's revenues, the total amount of revenues from each such customer, and the identity of the segment or segments reporting the revenues. A group of entities that the entity knows to be under common control generally will be considered a single customer for inclusion in this item. The federal government, a state government, a local government (for example, a county or municipality), or a foreign government each will generally be considered as a single customer for inclusion in this item.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9054-108599

+ Details

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) number in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017 USD ($)	Jun. 30, 2016	Mar. 31, 2017
Significant Accounting Policies [Line Items]
Number of natural gas distribution services customers					2
Segment Reporting, Disclosure of Major Customers	0	0	0	0
Excess tax benefit related to the share-based compensation provision			$ 5.2
Operating loss carryforward related to the share-based compensation provision			11.0
Prior period cash flow reclass related to the share-based compensation provision			$ 8.9