DEBT (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2017	Jun. 30, 2012
Long-term debt disclosure
Principal	$ 520,000		$ 520,000		$ 620,000
Unamortized Discount	(19,110)		(19,110)		(25,251)
Debt Issuance Costs	(7,404)		(7,404)		(8,579)
Total debt	493,486		493,486		586,170
Repayment of revolving credit facility			100,000
2019 Notes
Long-term debt disclosure
Principal	370,000		370,000		370,000
Unamortized Discount	(19,110)		(19,110)		(25,251)
Debt Issuance Costs	(1,986)		(1,986)		(2,646)
Total debt	348,904		348,904		342,103
Principal amount of debt issued						$ 370,000
Interest rate on convertible senior notes (as a percent)						2.875%
Interest expense recognized	6,100	$ 5,900	12,100	$ 11,700
Credit Facility
Long-term debt disclosure
Principal	150,000		150,000		250,000
Debt Issuance Costs	(5,418)		(5,418)		(5,933)
Total debt	144,582		144,582		$ 244,067
Interest expense recognized	1,800	$ 2,300	3,600	$ 4,300
Maximum availability under the revolving credit facility	1,000,000		1,000,000
Outstanding amount under credit facility	150,000		150,000
Available under the revolving credit facility	$ 850,000		$ 850,000
Effective interest rate (as percent)	3.24%		3.24%
Repayment of revolving credit facility	$ 50,000		$ 50,000
LIBOR | Credit Facility
Long-term debt disclosure
Basis spread on interest rate (as a percent)			1.75%