ACCUMULATED OTHER COMPREHENSIVE LOSS (Changes in Accumulated Other Comprehensive Loss by Component) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,188,202
Other comprehensive loss before tax effects	(16,666)
Tax effects	(80)
Other comprehensive income	(16,746)
Balance at end of period	1,145,526
Foreign Currency Translation
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(170,575)
Other comprehensive loss before tax effects	(16,551)
Tax effects	0
Other comprehensive income	(16,551)
Balance at end of period	(187,126)
Unrealized Losses on Available-For-Sale Securities
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(146)
Other comprehensive loss before tax effects	(115)
Tax effects	(80)
Other comprehensive income	(195)
Balance at end of period	(341)
Unfunded Pension Liability
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(1,686)
Other comprehensive loss before tax effects	0
Tax effects	0
Other comprehensive income	0
Balance at end of period	(1,686)
Total
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(172,407)
Balance at end of period	$ (189,153)