ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Accumulated other comprehensive income activity
Balance at the beginning of the period	$ 1,311,738
Balance at the end of the period	1,347,213
Foreign Currency
Accumulated other comprehensive income activity
Balance at the beginning of the period	(185,503)	$ (259,888)
Other comprehensive income (loss) before reclassifications	(43,283)	51,595
Net current-period other comprehensive income (loss)	(43,283)	51,595
Balance at the end of the period	(228,786)	(208,293)
Defined Benefit Pension Plans
Accumulated other comprehensive income activity
Balance at the beginning of the period	(64,595)	(59,775)
Amounts reclassified from accumulated other comprehensive income	2,699	1,775
Net current-period other comprehensive income (loss)	2,699	1,775
Balance at the end of the period	(61,896)	(58,000)
Derivatives
Accumulated other comprehensive income activity
Balance at the beginning of the period	(3,204)	(46)
Other comprehensive income (loss) before reclassifications	10,794
Amounts reclassified from accumulated other comprehensive income	(8,568)	14
Net current-period other comprehensive income (loss)	2,226	14
Balance at the end of the period	(978)	(32)
Accumulated Other Comprehensive Income/(Loss)
Accumulated other comprehensive income activity
Balance at the beginning of the period	(253,302)	(319,709)
Other comprehensive income (loss) before reclassifications	(32,489)	51,595
Amounts reclassified from accumulated other comprehensive income	(5,869)	1,789
Net current-period other comprehensive income (loss)	(38,358)	53,384
Balance at the end of the period	$ (291,660)	$ (266,325)