MORTGAGE SERVICING RIGHTS - Balance of loans serviced for others and fair value of mortgage servicing rights (Details) - Balance of loans serviced for others and fair value of mortgage servicing rights - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2014	Dec. 31, 2015
Residential mortgage loans serviced for others	$ 129,194	$ 137,186
Fair value of mortgage servicing rights	$ 1,037		$ 1,355