USE OF DERIVATIVES, OFFSETTING DISCLOSURES AND CHANGES IN OTHER COMPREHENSIVE INCOME BY COMPONENT- Changes in AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 227,422	$ 219,143	$ 293,910
Other comprehensive income (loss) before reclassifications	(119,877)	(13,776)	(91,681)
Amounts reclassified from accumulated other comprehensive income	28,550	22,055	16,914
Other comprehensive income (loss)	(91,327)	8,279	(74,767)
Ending Balance	136,095	227,422	219,143
Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(25,309)	(6,305)	(32,539)
Other comprehensive income (loss) before reclassifications	(21,675)	(41,059)	9,320
Amounts reclassified from accumulated other comprehensive income	28,550	22,055	16,914
Other comprehensive income (loss)	6,875	(19,004)	26,234
Ending Balance	(18,434)	(25,309)	(6,305)
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	252,731	225,448	326,449
Other comprehensive income (loss) before reclassifications	(98,202)	27,283	(101,001)
Amounts reclassified from accumulated other comprehensive income	0	0	0
Other comprehensive income (loss)	(98,202)	27,283	(101,001)
Ending Balance	$ 154,529	$ 252,731	$ 225,448