FAIR VALUE - GAINS AND LOSSES (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair value gain loss change in fair value
Aggregate fair value	$ 4,083				$ 6,388				$ 3,506				$ 4,083	$ 6,388	$ 3,506	$ 10,614
Unrealized gain													3,915	2,440	6,979
Interest income	32,466	$ 31,424	$ 31,058	$ 29,022	29,477	$ 28,442	$ 27,550	$ 27,304	$ 26,739	$ 28,539	$ 28,767	$ 29,130	123,970	112,773	113,175
Mortgage loans held for sale
Fair value gain loss change in fair value
Aggregate fair value	4,083				6,388								4,083	6,388
Contractual balance	$ 3,993				$ 6,265								3,993	6,265
Unrealized gain													90	123
Interest income													219	183	471
Change in fair value													(33)	34	(488)
Total included in earnings													$ 186	$ 217	$ (17)