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	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2014	Dec. 31, 2015
Residential mortgage loans serviced for others	$ 125,988	$ 132,201
Fair value of mortgage servicing rights	$ 962		$ 1,429