ACCUMULATED OTHER COMPREHENSIVE INCOME (Schedule of Components) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 1,556,873
Other comprehensive income/(loss) before reclassifications	(5,968)	$ (12,979)
Amounts reclassified from accumulated other comprehensive income (loss)	(124)	(199)
Net other comprehensive income/(loss)	(6,092)	(13,178)
Ending balance	1,542,567	1,556,873
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	239	13,417
Ending balance	(5,853)	239
Foreign currency translation gains
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,010)	15,975
Other comprehensive income/(loss) before reclassifications	4,680	(16,985)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Net other comprehensive income/(loss)	4,680	(16,985)
Ending balance	3,670	(1,010)
Net investment hedges of New Zealand subsidiary
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	1,321	1,665
Other comprehensive income/(loss) before reclassifications	0	(344)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Net other comprehensive income/(loss)	0	(344)
Ending balance	1,321	1,321
Cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	21,965	16,184
Other comprehensive income/(loss) before reclassifications	(10,648)	5,944
Amounts reclassified from accumulated other comprehensive income (loss)	(236)	(163)
Net other comprehensive income/(loss)	(10,884)	5,781
Ending balance	11,081	21,965
Cash flow hedges | Interest rate swaps
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income/(loss) before reclassifications	11,500
Employee benefit plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(22,037)	(20,407)
Other comprehensive income/(loss) before reclassifications	0	(1,594)
Amounts reclassified from accumulated other comprehensive income (loss)	112	(36)
Net other comprehensive income/(loss)	112	(1,630)
Ending balance	$ (21,925)	$ (22,037)