FAIR VALUE (Activity for Assets and Liabilities Measured on Recurring Level 3 Basis) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Reclassification of net fair value gains on sold/redeemed bonds	$ 1,851	$ 5,080	$ 26,115	$ 5,080
Net unrealized gains (losses) arising during the period	961	1,025	997	2,143
Reclassification of realized losses (gains) to the Consolidated Statements of Operations related to bond investments assessed as other-than-temporary-impairment ("OTTI")				100
ASU 2017-08
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	(300)		(300)
Investments in Debt Securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Reclassification of net fair value gains on sold/redeemed bonds	1,900		26,100
Net unrealized gains (losses) arising during the period	1,000	1,000	1,000
Fair Value, Inputs, Level 3 [Member] \| Derivative Liabilities [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning period		(44)		(46)
Net (losses) gains included in earnings		(26)		(24)
Balance at ending period		(70)		(70)
Fair Value, Inputs, Level 3 [Member] \| Investments in Debt Securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at start of period	35,236	162,261	97,190	143,604
Net (losses) gain included in earnings				(6)
Net change in AOCI (1)	(890)	(3,914)	(25,118)	(2,931)
Impact from deconsolidation				17,997
Impacts from sales/redemptions	(264)	(10,364)	(37,633)	(10,364)
Impacts from settlements	39	(175)	(318)	(492)
Balance at end of period	$ 34,121	147,808	34,121	147,808
Reclassification of net fair value gains on sold/redeemed bonds				5,100
Fair Value, Inputs, Level 3 [Member] \| Derivative Assets [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning period		2,747	1,130	2,347
Net (losses) gains included in earnings		(158)	(195)	242
Impact from settlements			$ (935)
Balance at ending period		$ 2,589		$ 2,589

Fair Value, Measurement with Unobservable Inputs Reconciliation, Increase (Decrease) from Deconsolidation

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