COMMITMENTS AND CONTINGENCIES - Lease Commitments (Details) $ in Thousands, ft² in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
COMMITMENTS AND CONTINGENCIES
Area of lease (in square feet) | ft²	2.7
Obligation for payments under leases
2017	$ 20,908
2018	26,120
2019	16,100
2020	17,090
2021	7,170
Thereafter	15,009
Total obligations under operating leases	102,397
Rent expense
Rent expense	$ 19,800	$ 17,000	$ 15,000