SEGMENTS, GEOGRAPHIC INFORMATION AND SIGNIFICANT CUSTOMERS GEOGRAPHIC INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues from External Customer [Line Items]
Revenue	$ 137,380	$ 128,094	$ 283,293	$ 262,577
Income from operations	27,714	33,428	61,512	70,751
Sales Revenue [Member]
Revenues from External Customer [Line Items]
Number of major customers (in major customers)	0	0	0	0
United States [Member]
Revenues from External Customer [Line Items]
Revenue	125,906	117,187	259,489	239,698
Income from operations	27,083	32,314	60,127	67,957
International [Member]
Revenues from External Customer [Line Items]
Revenue	11,561	11,060	24,003	23,215
Income from operations	631	1,114	1,385	2,794
Inter-regional Elimination [Member]
Revenues from External Customer [Line Items]
Revenue	$ (87)	$ (153)	$ (199)	$ (336)