PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS CHANGE IN PROJECTED BENEFIT OBLIGATION AND PLAN ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	$ (11,146)
Fair Value of Plan Assets, balance beginning of year			$ 1,900,372	$ 1,900,372
Defined Benefit Plan, Plan Assets, Contributions by Employer				13,616	$ 14,163	$ 17,462
Fair Value of Plan Assets, balance end of year	1,903,901			1,903,901	1,900,372
Accrued pension and other postretirement benefits, noncurrent	(483,887)			(483,887)	(592,134)
Other postretirement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement				0	0
PBO balance at beginning of year			$ 164,128	164,128	179,901
Defined Benefit Plan, Service Cost				391	716	1,186
Defined Benefit Plan, Interest Cost				4,393	4,987	7,669
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)				(17,780)	(4,865)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment				20,042	0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits				0	0	0
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)				0	0
PBO balance at end of year	119,164			119,164	164,128	179,901
Defined Benefit Plan, Accumulated Benefit Obligation	$ 119,164			$ 119,164	$ 164,128
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.93%		3.73%	3.93%	3.86%
Fair Value of Plan Assets, balance beginning of year			$ 0	$ 0	$ 0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)				0	0
Defined Benefit Plan, Plan Assets, Payment for Settlement				0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer				11,926	16,611
Defined Benefit Plan, Benefits Paid (Deprecated 2017-01-31)				(12,811)	(17,990)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)				0	0
Fair Value of Plan Assets, balance end of year	$ 0			0	0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(119,164)			(119,164)	(164,128)
Assets for Plan Benefits, Defined Benefit Plan	0			0	0
Liability, Defined Benefit Plan, Current	(11,584)			(11,584)	(15,983)
Accrued pension and other postretirement benefits, noncurrent	(107,580)			(107,580)	(148,145)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	(75,261)			(75,261)	(33,920)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	(19,151)			(19,151)	(64,756)
Deferred Tax Assets, Other Comprehensive Loss	(42,016)			(42,016)	(36,412)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	(52,396)			(52,396)	(62,264)
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant				885	1,379
Pension benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement				3,233	0
PBO balance at beginning of year			2,346,990	2,346,990	2,430,315
Defined Benefit Plan, Service Cost				4,505	6,538	10,902
Defined Benefit Plan, Interest Cost				75,189	72,638	88,708
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)				19,110	14,104
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	(2,297)	$ (3,314)	$ (2,863)	1,939	121
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits				0	0	724
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)				5,471	6,010
PBO balance at end of year	2,277,816			2,277,816	2,346,990	2,430,315
Defined Benefit Plan, Accumulated Benefit Obligation	2,272,505			$ 2,272,505	$ 2,336,062
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Range				2.65 - 4.01%	2.87 - 4.06%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate			3.86%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligations, Rate of Compensation Increase Range				3.50 - 4.50%	3.50 - 4.50%
Fair Value of Plan Assets, balance beginning of year			$ 1,900,372	$ 1,900,372	$ 1,925,685
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)				164,281	149,103
Defined Benefit Plan, Plan Assets, Payment for Settlement				(3,233)	0
Defined Benefit Plan, Plan Assets, Contributions by Employer				5,124	2,146
Defined Benefit Plan, Benefits Paid (Deprecated 2017-01-31)				(168,464)	(170,900)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)				5,634	(5,846)
Fair Value of Plan Assets, balance end of year	1,903,901			1,903,901	1,900,372	$ 1,925,685
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(373,915)			(373,915)	(446,618)
Assets for Plan Benefits, Defined Benefit Plan	3,155			3,155	1,465
Liability, Defined Benefit Plan, Current	(764)			(764)	(4,094)
Accrued pension and other postretirement benefits, noncurrent	(376,306)			(376,306)	(443,989)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	(3,978)			(3,978)	(4,852)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	570,933			570,933	577,605
Deferred Tax Assets, Other Comprehensive Loss	(205,250)			(205,250)	(209,696)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	$ 361,705			361,705	363,057
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant				$ 187	$ 184