USE OF DERIVATIVES, OFFSETTING DISCLOSURES AND CHANGES IN OTHER COMPREHENSIVE INCOME BY COMPONENT - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance			$ 1,247,687
Other comprehensive income (loss) before reclassifications	$ (5,245)		(10,955)
Amounts reclassified from accumulated other comprehensive income	(3,213)		(2,207)
Other comprehensive income (loss)	(8,458)	$ (1,670)	(13,162)	$ (15,362)
Ending Balance	1,273,403		1,273,403
Unrealized Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	2,871		151
Other comprehensive income (loss) before reclassifications	1,827		3,541
Amounts reclassified from accumulated other comprehensive income	(3,213)		(2,207)
Other comprehensive income (loss)	(1,386)		1,334
Ending Balance	1,485		1,485
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	98,211		105,635
Other comprehensive income (loss) before reclassifications	(7,072)		(14,496)
Amounts reclassified from accumulated other comprehensive income	0		0
Other comprehensive income (loss)	(7,072)		(14,496)
Ending Balance	91,139		91,139
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	101,082		105,786
Ending Balance	$ 92,624		$ 92,624