BASIS OF PRESENTATION - Statement of Comprehensive Income Impact (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	$ (191,327)	$ (46,282)	$ (211,638)	$ (76,398)
Amortization of accumulated actuarial gains and prior service costs, pension	119	583	239	1,177
Adjustments to accumulated actuarial gains and transition obligations, pension	148	165	(45)	301
Amortization of accumulated actuarial gains, transition obligations, and prior service costs, postretirement medical benefits	969	965	1,938	1,929
Tax effect of other comprehensive income	(857)	(1,247)	(902)	(2,205)
Foreign currency translation adjustment (losses) gains	(5,255)	5,926	(12,544)	8,029
Unrealized and realized (losses) gains on available-for-sale debt securities	(246)	386	(276)	1,196
Other comprehensive income, net of income taxes	(5,122)	6,778	(11,590)	10,427
Comprehensive loss	(196,449)	(39,504)	(223,228)	(65,971)
Less: Comprehensive loss attributable to noncontrolling interest	(5,260)	(138)	(5,982)	(637)
Comprehensive loss attributable to common shareholders	$ (191,189)	(39,366)	$ (217,246)	(65,334)
As Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		(50,520)		(87,821)
Amortization of accumulated actuarial gains and prior service costs, pension				1,177
Adjustments to accumulated actuarial gains and transition obligations, pension				301
Amortization of accumulated actuarial gains, transition obligations, and prior service costs, postretirement medical benefits				1,929
Tax effect of other comprehensive income				(1,819)
Foreign currency translation adjustment (losses) gains				8,029
Unrealized and realized (losses) gains on available-for-sale debt securities				1,196
Other comprehensive income, net of income taxes				10,813
Comprehensive loss				(77,008)
Less: Comprehensive loss attributable to noncontrolling interest				(637)
Comprehensive loss attributable to common shareholders				(76,371)
Accounting Standards Update 2014-09 | Adjustments for New Revenue Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		$ 4,238		11,423
Amortization of accumulated actuarial gains and prior service costs, pension				0
Adjustments to accumulated actuarial gains and transition obligations, pension				0
Amortization of accumulated actuarial gains, transition obligations, and prior service costs, postretirement medical benefits				0
Tax effect of other comprehensive income				386
Foreign currency translation adjustment (losses) gains				0
Unrealized and realized (losses) gains on available-for-sale debt securities				0
Other comprehensive income, net of income taxes				(386)
Comprehensive loss				11,037
Less: Comprehensive loss attributable to noncontrolling interest				0
Comprehensive loss attributable to common shareholders				$ 11,037