PENSIONS - Net Periodic Benefit Costs (Details) - Pensions - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of net periodic benefit cost:
Service cost	$ 250	$ 313	$ 302
Interest cost	1,687	1,901	2,051
Expected return on plan assets	(926)	(843)	(806)
Recognized actuarial loss	1,392	1,182	1,060
Net periodic benefit cost	2,403	2,553	$ 2,607
Estimated net loss for defined benefit pension plans to be amortized from accumulated other comprehensive income into net periodic benefit cost in next fiscal year	$ 1,400	$ 1,200

Amount of gain (loss), recognized immediately as component of net periodic benefit (cost) credit, for change in value of benefit obligation or plan assets from experience different from that assumed, change in actuarial assumption, or consequence of temporarily deviating from substantive plan. Includes, but is not limited to, amount in excess of ten percent of greater of fair value of plan assets or benefit obligation.

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Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

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Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of net periodic benefit cost (credit) for defined benefit plan.

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- Definition

Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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