SEGMENT INFORMATION - SCHEDULE OF REVENUE AND LONG-LIVED ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue and Long-lived Assets by Geography
Revenue	$ 848,728	$ 838,561	$ 771,132	$ 772,512	$ 830,754	$ 782,231	$ 756,315	$ 740,247	$ 3,230,933	$ 3,109,547	$ 3,022,987
Long-lived assets (excluding goodwill and intangible assets)	302,817				302,459				302,817	302,459
United States
Revenue and Long-lived Assets by Geography
Revenue									2,376,035	2,146,189	2,081,485
Long-lived assets (excluding goodwill and intangible assets)	279,913				281,879				279,913	281,879
All Other Countries
Revenue and Long-lived Assets by Geography
Revenue									854,898	963,358	$ 941,502
Long-lived assets (excluding goodwill and intangible assets)	$ 22,904				$ 20,580				$ 22,904	$ 20,580