SUBSEQUENT EVENTS (Details) - Subsequent event - Medium-term notes	Jan. 31, 2018 USD ($)
Series 2017A-2, Due January 2025
Subsequent Event [Line Items]
Private placement	$ 25,000,000.0
Stated interest rate	3.32%
Series 2017B-2, Due January 2028
Subsequent Event [Line Items]
Private placement	$ 25,000,000.0
Stated interest rate	3.56%

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant