FAIR VALUE (Activity for Assets and Liabilities Measured on Recurring Level 3 Basis) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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	$ 20,693	$ 0	$ 24,264	$ 0
Net unrealized gains (losses) arising during the period	(370)	4,465	36	1,118
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	20,700		24,300
Net unrealized gains (losses) arising during the period	400	4,500
Level 3 \| Derivative Liabilities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning period		(48)		(46)
Net (losses) gains included in earnings		4		2
Balance at ending period		(44)		(44)
Level 3 \| Investments in Debt Securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at start of period	81,102	157,824	97,190	143,604
Net (losses) gain included in earnings				(6)
Net change in AOCI (1)	(21,063)	4,465	(24,228)	983
Impact from deconsolidation				17,997
Impacts from sales/redemptions	(24,779)		(37,369)
Impacts from settlements	(24)	(28)	(357)	(317)
Balance at end of period	35,236	162,261	35,236	162,261
Net unrealized gains (losses) arising during the period				1,100
Reclassification of realized losses (gains) to the Consolidated Statements of Operations related to bond investments assessed as other-than-temporary-impairment ("OTTI")				100
Level 3 \| Derivative Assets
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning period			1,130
Balance at start of period	776	2,250		2,347
Net (losses) gains included in earnings			(195)
Net (losses) gain included in earnings	(42)	497		400
Impact from settlements			$ (935)
Impacts from settlements	$ (734)
Balance at end of period		$ 2,747		$ 2,747

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

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