SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - COMPUTER SOFTWARE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Capitalized software, net	$ 95,301	$ 68,004
Computer Software
Property, Plant and Equipment [Line Items]
Capitalized software, net	95,301	68,004
Capitalized computer software, accumulated amortization	$ 322,807	$ 304,057
Computer Software | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Computer Software | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years