INCOME TAXES (Effective Income Tax Reconciliation) (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
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Statutory federal tax									$ 37,125	$ 29,564	$ 26,102
Increase/ (decrease) in taxes resulting from:
State taxes, net of federal benefit									341	311	368
Provision adjustment for current year uncertain tax position									0	(1,220)	0
Effect of permanent differences									7,314	8,589	2,524
Stock-based compensation									7,591	3,782	1,948
Rate differential between U.S. and foreign									(31,094)	(24,772)	(17,279)
Change in foreign tax rate									9	754	(59)
Change in valuation allowance									0	149	489
Other									328	155	683
Total	$ 7,095	$ 5,800	$ 5,209	$ 3,510	$ 6,159	$ 3,338	$ 3,587	$ 4,228	$ 21,614	$ 17,312	$ 14,776