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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	$ 221,586		$ 227,422
Other comprehensive income (loss) before reclassifications	(15,347)		(27,631)
Amounts reclassified from accumulated other comprehensive income	6,863		13,311
Other comprehensive income (loss)	(8,484)	$ 8,878	(14,320)	$ 17,637
Ending Balance	213,102		213,102
Gains and Losses on Cash Flow Hedges [Member]
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	(37,252)		(25,309)
Other comprehensive income (loss) before reclassifications	3,400		(14,991)
Amounts reclassified from accumulated other comprehensive income	6,863		13,311
Other comprehensive income (loss)	10,263		(1,680)
Ending Balance	(26,989)		(26,989)
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	258,838		252,731
Other comprehensive income (loss) before reclassifications	(18,747)		(12,640)
Amounts reclassified from accumulated other comprehensive income	0		0
Other comprehensive income (loss)	(18,747)		(12,640)
Ending Balance	$ 240,091		$ 240,091