COMPREHENSIVE INCOME - Narrative (Details) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain reclassified from accumulated other comprehensive income	$ 6,242
Other Expense \| Accumulated Net Investment Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain reclassified from accumulated other comprehensive income	$ 6,200

Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581

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