Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6578-128477

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details)	1 Months Ended			12 Months Ended
	Oct. 31, 2018 USD ($)	May 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2018 operating_segment
Related Party Transaction [Line Items]
Number of operating segments \| operating_segment				2
Natural Gas Storage Facility
Related Party Transaction [Line Items]
Percentage of voting interest acquired		100.00%	80.00%	80.00%
Consideration		$ 12,200,000	$ 24,800,000.0
Subsequent Event \| Natural Gas Storage Facility
Related Party Transaction [Line Items]
Percentage of voting interest acquired	20.00%
Consideration	$ 17,000,000.0