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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance			$ 1,247,687
Other comprehensive income (loss) before reclassifications	$ (17,907)		(5,815)
Amounts reclassified from accumulated other comprehensive income	(655)		1,006
Other comprehensive income (loss)	(18,562)	$ 598	(4,809)	$ (13,692)
Ending Balance	1,245,583		1,245,583
Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	9,908		151
Other comprehensive income (loss) before reclassifications	(6,487)		1,609
Amounts reclassified from accumulated other comprehensive income	(655)		1,006
Other comprehensive income (loss)	(7,142)		2,615
Ending Balance	2,766		2,766
Unrealized Gains and Losses on Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	109,631		105,635
Other comprehensive income (loss) before reclassifications	(11,420)		(7,424)
Amounts reclassified from accumulated other comprehensive income	0		0
Other comprehensive income (loss)	(11,420)		(7,424)
Ending Balance	98,211		98,211
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	119,539		105,786
Ending Balance	$ 100,977		$ 100,977