COMMITMENTS AND CONTINGENCIES (Material Components Underlying Estimated Loss for Cleanup, Remediation and Restoration) (Details) $ in Millions	Jun. 30, 2017 USD ($)
Estimated total loss of crude oil release	$ 1,215.0
Response Personnel and Equipment [Member]
Estimated total loss of crude oil release	547.3
Environmental Consultants [Member]
Estimated total loss of crude oil release	224.3
Professional, Regulatory, Fines and Penalties and Other [Member]
Estimated total loss of crude oil release	$ 443.4

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

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