SEGMENT AND GEOGRAPHIC INFORMATION - Revenue by Geographic Region (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 349,019	$ 330,399	$ 295,623
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	212,756	202,323	171,176
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	80,919	80,844	71,526
APAC [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	40,244	33,957	39,862
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 15,100	$ 13,275	$ 13,059