COMMITMENTS AND CONTINGENCIES - Minimum lease (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies
Rental expense	$ 13,200	$ 14,300	$ 13,200
Future minimum payments under leases
2016	9,248
2017	9,625
2018	9,119
2019	9,196
2020	9,349
Later years	50,173
Total future minimum lease payments	$ 96,710