INCOME TAXES (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
Tax benefit, re-measurement of net deferred tax liabilities, Tax Cuts and Jobs Act of 2017	$ 43,400
Income tax expense, Tax Cuts and Jobs Act of 2017	5,500
Income tax expense, to be paid within one year, Tax Cuts and Jobs Act of 2017	$ 400
Decrease in effective income tax rate during the period	486.20%
Effective income tax rate reconciliation, foreign income tax rate differential, increase (decrease), amount	$ 1,200	$ (800)
Effective foreign income tax rate	15.70%	12.70%
Increase (decrease) in effective foreign income tax rate during period	2.90%	(2.10%)
Operating loss carryforwards, not subject to expiration	$ 25,400
Deferred tax assets, valuation allowance	7,961	$ 3,604	$ 4,900
Deferred tax assets, gross	96,499	78,227	82,500
Valuation allowance, period increase	4,400	1,300
Unrecognized tax benefits that would impact effective tax rate	400
Amount of unrecorded benefit reasonably possible to be recognized	100
Penalties and interest expense	0	0	0
Penalties and interest accrued	0	$ 0	$ 0
Federal
Income Tax [Line Items]
Operating loss carryforwards	148,200
Foreign Tax Authority
Income Tax [Line Items]
Operating loss carryforwards	26,400
Operating loss carryforwards, subject to expiration	$ 1,000
Foreign Tax Authority | Switzerland
Income Tax [Line Items]
Reduced corporate tax rate	8.00%
State and Local Jurisdiction
Income Tax [Line Items]
Operating loss carryforwards	$ 28,200