USE OF DERIVATIVE FINANCIAL INSTRUMENTS, OFFSETTING DISCLOSURES AND CHANGES IN OTHER COMPREHENSIVE INCOME BY COMPONENT - Changes in AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	$ 236,780		$ 219,143
Other comprehensive income (loss) before reclassifications	(10,623)		(3,092)
Amount of loss reclassified from Accumulated other comprehensive income related to the effective portion of active positions	5,826	3,698	15,932	13,548
Other comprehensive income (loss)	(4,797)	(34,708)	12,840	(81,353)
Ending Balance	231,983		231,983
Gains and Losses on Cash Flow Hedges [Member]
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	(21,853)		(6,305)
Other comprehensive income (loss) before reclassifications	97		(25,557)
Amount of loss reclassified from Accumulated other comprehensive income related to the effective portion of active positions	5,826		15,932
Other comprehensive income (loss)	5,923		(9,625)
Ending Balance	(15,930)		(15,930)
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	258,633		225,448
Other comprehensive income (loss) before reclassifications	(10,720)		22,465
Amount of loss reclassified from Accumulated other comprehensive income related to the effective portion of active positions	0		0
Other comprehensive income (loss)	(10,720)		22,465
Ending Balance	$ 247,913		$ 247,913