GOODWILL AND OTHER INTANGIBLE ASSETS - Changes in Carrying Amount of Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill
Balance at beginning of period	$ 187,591	$ 187,591
Translation adjustment	0	0
Balance at end of period	194,052	187,591	$ 187,591
Other Intangible Assets
Balance at beginning of period	78,525	94,831
Translation adjustment	(917)	960
Amortization	(16,586)	(17,266)	(18,061)
Balance at end of period	67,207	78,525	94,831
Total
Balance at beginning of period	266,116	282,422
Translation adjustment	(917)	960
Amortization	(16,586)	(17,266)	(18,061)
Balance at end of period	261,259	$ 266,116	$ 282,422
ASI
Goodwill
Acquisition of ASI	6,461
Other Intangible Assets
Acquisition of ASI	6,185
Total
Acquisition of ASI	$ 12,646