DEBT (Details)			1 Months Ended	12 Months Ended
	Apr. 28, 2017 USD ($)	May 08, 2011	May 31, 2015 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)
Debt Disclosure [Line Items]
Proceeds from issuance of senior notes, net of issuance costs				$ 0	$ 0	$ 488,401,000
Credit facility expiration date				May 09, 2020
Commitment fee percentage				0.37%
Outstanding borrowings under line of credit				$ 0
EBITDA	3.25	3
Minimum required liquid funds				$ 300,000,000.0
Line Of Credit Facility Interest Rate Spread Below The Banks Announced Prime Rate
Debt Disclosure [Line Items]
Basis spread of variable rate				1.20%
Line Of Credit Facility Interest Rate Spread Above A Daily One Month LIBOR Rate
Debt Disclosure [Line Items]
Basis spread of variable rate				1.40%
Senior notes | 5.50% Senior Notes
Debt Disclosure [Line Items]
Principal amount of debt issued			$ 500,000,000.0
Stated interest rate			5.50%	5.50%
Proceeds from issuance of senior notes, net of issuance costs			$ 488,400,000
Debt issuance costs			$ 11,600,000
Debt redemption percentage price, Specified Price			105.50%
Repurchase price, percentage of principal amount			101.00%
Fair Value | Level 2 | Senior notes | 5.50% Senior Notes
Debt Disclosure [Line Items]
Long term debt, 5.50% Senior Notes				$ 497,095,000	505,150,000
Carrying Value | Level 2 | Senior notes | 5.50% Senior Notes
Debt Disclosure [Line Items]
Long term debt, 5.50% Senior Notes				$ 492,509,000	$ 491,059,000
Minimum | Senior notes | 5.50% Senior Notes
Debt Disclosure [Line Items]
Debt redemption notice period			30 days
Maximum | Senior notes | 5.50% Senior Notes
Debt Disclosure [Line Items]
Debt redemption notice period			60 days
Percentage of debt redeemed			35.00%
Revolving Credit Facility
Debt Disclosure [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000.0