TAXES Narrative (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Mar. 31, 2019 USD ($) aircraft	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		$ 39,554	$ 9,140
Deferred Income Tax Expense (Benefit)		(16,811)	(45,745)	$ 12,638
Deferred Tax Assets, Valuation Allowance		128,214	71,987	$ 74,727	$ 29,373
Deferred Tax Assets, Capital Loss Carryforwards		$ 4,200	$ 0
Effective Income Tax Rate Reconciliation, Percent		0.00%	13.50%	(22.70%)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount		$ 51,000	$ 53,000	$ 37,000
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		(19,000)
Effective Income Tax Rate Reconciliation, One-time Non-cash Transition, Amount		$ (30,600)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%	21.00%	31.60%	35.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount			$ (27,000)	$ (8,700)
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount		$ (11,600)	(52,900)
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount			22,600
Effective Income Tax Rate Reconciliation, Change in Foreign Tax Credit Valuation Allowances, Amount			22,800
Number of aircraft involved in intercompany leasing transaction | aircraft		11
Remaining useful life of an intercompany leasing transaction		13 years
Tax benefit from intercompany leasing transaction				2,400
Unrecognized tax benefits period increase decrease		$ (2,300)	5,400	200
Unrecognized tax benefit, Interest and penalties		0	100	200
Unrecognized Tax Benefits		4,337	6,682	1,332
Unremitted foreign earnings reinvested abroad		442,000
Income taxes paid		19,400	26,700	$ 28,100
Interest Expense [Member]
Operating Loss Carryforwards [Line Items]
Deferred Income Tax Expense (Benefit)		(85,000)
Year 2021
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		6,600
Year 2022
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		4,000
Year 2023
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		200
Year 2024
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		15,600
Year 2025
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		13,200
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards		145,000
Domestic Tax Authority [Member] | Year 2037
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		800
Domestic Tax Authority [Member] | Year 2038
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		6,500
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration		137,800
State and Local Jurisdiction [Member] | Valuation Allowance, Operating Loss Carryforwards
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Valuation Allowance		12,448	12,337
State and Local Jurisdiction [Member] | Year 2022
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		200,100
Foreign Tax Authority [Member] | Valuation Allowance, Operating Loss Carryforwards
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Valuation Allowance		$ 76,212	$ 50,510