USE OF DERIVATIVES, OFFSETTING DISCLOSURES AND CHANGES IN OTHER COMPREHENSIVE INCOME (LOSS) BY COMPONENT - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 1,022,388	$ 1,168,856	$ 1,059,063	$ 1,238,876
Other comprehensive income	(13,042)	(30,353)	46,765	(66,727)
Ending Balance	1,071,756	1,121,093	1,071,756	1,121,093
Unrealized Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(26,019)		6,200
Other comprehensive loss before reclassifications	(7,648)		(22,945)
Amounts reclassified from accumulated other comprehensive income	(2,702)		(19,624)
Other comprehensive income	(10,350)		(42,569)
Ending Balance	(36,369)		(36,369)
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	64,780		(27,246)
Other comprehensive loss before reclassifications	(2,692)		89,334
Amounts reclassified from accumulated other comprehensive income	0		0
Other comprehensive income	(2,692)		89,334
Ending Balance	62,088		62,088
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	38,761	25,744	(21,046)	62,118
Other comprehensive loss before reclassifications	(10,340)		66,389
Amounts reclassified from accumulated other comprehensive income	(2,702)		(19,624)
Other comprehensive income	(13,042)		46,765
Ending Balance	$ 25,719	$ (4,609)	$ 25,719	$ (4,609)