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
	Mar. 31, 2015	Mar. 31, 2014
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	$ 227,422
Other comprehensive income (loss) before reclassifications	(12,284)
Amounts reclassified from accumulated other comprehensive income	6,448
Other comprehensive income (loss)	(5,836)	8,759
Ending Balance	221,586
Gains and Losses on Cash Flow Hedges [Member]
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	(25,309)
Other comprehensive income (loss) before reclassifications	(18,391)
Amounts reclassified from accumulated other comprehensive income	6,448
Other comprehensive income (loss)	(11,943)
Ending Balance	(37,252)
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated other comprehensive income (loss) [Line Items]
Beginning Balance	252,731
Other comprehensive income (loss) before reclassifications	6,107
Amounts reclassified from accumulated other comprehensive income	0
Other comprehensive income (loss)	6,107
Ending Balance	$ 258,838