USE OF DERIVATIVES, OFFSETTING DISCLOSURES AND CHANGES IN OTHER COMPREHENSIVE INCOME BY COMPONENT - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 1,238,876
Other comprehensive (loss) income	$ (30,353)	$ (8,458)	(66,727)	$ (13,162)
Ending Balance	1,121,093		1,121,093
Unrealized Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	41,065		16,874
Other comprehensive income (loss) before reclassifications	7,580		46,385
Amounts reclassified from accumulated other comprehensive income	(11,162)		(25,776)
Other comprehensive (loss) income	(3,582)		20,609
Ending Balance	37,483		37,483
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(15,321)		45,244
Other comprehensive income (loss) before reclassifications	(26,771)		(87,336)
Amounts reclassified from accumulated other comprehensive income	0		0
Other comprehensive (loss) income	(26,771)		(87,336)
Ending Balance	(42,092)		(42,092)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	25,744		62,118
Other comprehensive income (loss) before reclassifications	(19,191)		(40,951)
Amounts reclassified from accumulated other comprehensive income	(11,162)		(25,776)
Other comprehensive (loss) income	(30,353)		(66,727)
Ending Balance	$ (4,609)		$ (4,609)