CONTINGENCIES, COMMITMENTS, AND GUARANTEES - SO Litigation (Details)	Dec. 31, 2017 lawsuit
Shareholder Derivative Lawsuits \| Pending Litigation
Loss Contingencies [Line Items]
Number of claims	2

Number of pending claims pertaining to a loss contingency.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14435-108349

Name:	us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant