LONG-TERM DEBT (Details) - Credit Facility 2017 - USD ($) $ in Thousands	May 24, 2017	Mar. 31, 2019	Dec. 31, 2018
Revolving credit facility
Debt Instrument [Line Items]
Maturity date	May 24, 2022
Revolving credit facility | Federal Funds Open Rate
Debt Instrument [Line Items]
Variable interest rate spread	0.50%
Revolving credit facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	1.00%
Revolving credit facility | U.S. dollars
Debt Instrument [Line Items]
Line of credit, current borrowing capacity	$ 300,000
Line of credit, maximum borrowing capacity	400,000
Outstanding debt		$ 25,000	$ 25,000
Interest rate		3.49%	3.51%
Available borrowing capacity		$ 274,626	$ 274,618
Revolving credit facility | U.S. dollars | Maximum
Debt Instrument [Line Items]
Line of credit, current borrowing capacity		300,000	300,000
Revolving credit facility | Other currencies, excluding U.S. dollars
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity	$ 100,000
Standby letters of credit
Debt Instrument [Line Items]
Irrevocable standby letters of credit		$ 374	$ 382