EMPLOYEE BENEFIT PLANS Schedule of Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	$ 478,350	$ 508,375	$ 455,539
Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	26,191	26,373
Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	386,876	482,002
Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	65,283	0
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	26,191	26,373
Cash and cash equivalents | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	26,191	26,373
Cash and cash equivalents | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Cash and cash equivalents | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Cash plus
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	84,438	105,070
Cash plus | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Cash plus | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	84,438	105,070
Cash plus | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Equity investments - U.K.
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	2,476	1,683
Equity investments - U.K. | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Equity investments - U.K. | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	2,476	1,683
Equity investments - U.K. | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Equity investments - Non-U.K.
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	1,303	151,923
Equity investments - Non-U.K. | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Equity investments - Non-U.K. | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	1,303	151,923
Equity investments - Non-U.K. | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Insurance Linked Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	25,279
Insurance Linked Securities | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0
Insurance Linked Securities | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0
Insurance Linked Securities | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	25,279
Illiquid credit
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	40,004
Illiquid credit | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0
Illiquid credit | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0
Illiquid credit | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	40,004
Property
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets		15,852
Property | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets		0
Property | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets		15,852
Property | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets		0
Diversified growth (absolute return) funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	86,001	1,824
Diversified growth (absolute return) funds | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Diversified growth (absolute return) funds | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	86,001	1,824
Diversified growth (absolute return) funds | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Government debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	138,384	124,428
Government debt securities | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Government debt securities | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	138,384	124,428
Government debt securities | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	74,274	81,222
Corporate debt securities | Fair value, inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Corporate debt securities | Fair value, inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	74,274	81,222
Corporate debt securities | Fair value, inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	$ 0	$ 0