USE OF DERIVATIVE FINANCIAL INSTRUMENTS, OFFSETTING DISCLOSURES AND CHANGES IN OTHER COMPREHENSIVE INCOME BY COMPONENT - Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	$ 213,102		$ 227,422
Other comprehensive income (loss) before reclassifications	(32,365)		(59,996)
Amounts reclassified from accumulated other comprehensive income	7,183		20,494
Other comprehensive income (loss)	(25,182)	$ (4,797)	(39,502)	$ 12,840
Ending Balance	187,920		187,920
Gains and Losses on Cash Flow Hedges [Member]
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	(26,989)		(25,309)
Other comprehensive income (loss) before reclassifications	(21,235)		(36,226)
Amounts reclassified from accumulated other comprehensive income	7,183		20,494
Other comprehensive income (loss)	(14,052)		(15,732)
Ending Balance	(41,041)		(41,041)
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	240,091		252,731
Other comprehensive income (loss) before reclassifications	(11,130)		(23,770)
Amounts reclassified from accumulated other comprehensive income	0		0
Other comprehensive income (loss)	(11,130)		(23,770)
Ending Balance	$ 228,961		$ 228,961