FINANCING ARRANGEMENTS - Revolving Credit Facility (Details) - USD ($)	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Debt Instrument [Line Items]
Long-term debt	$ 90,000,000	$ 90,000,000
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt	90,000,000	90,000,000
Maximum borrowing capacity	$ 295,000,000.0	295,000,000.0
Debt term	5 years
Increase limit for revolving credit commitments	$ 150,000,000.0
Revolving credit facility remaining borrowing capacity	183,500,000
Line of Credit | Letter of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	30,000,000.0
Line of Credit | Swingline Loan
Debt Instrument [Line Items]
Maximum borrowing capacity	30,000,000.0
Line of Credit | Standby Letters of Credit
Debt Instrument [Line Items]
Long-term line of credit	$ 21,500,000
Revolving Credit Facility, June 2011 | Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument face amount		200,000,000.0
Interest expense		$ 100,000
Minimum | Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Facility fee (as a percent)	0.25%
Maximum | Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Facility fee (as a percent)	0.40%
London Interbank Offered Rate (LIBOR) | Minimum | Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread (as a percent)	1.25%
London Interbank Offered Rate (LIBOR) | Maximum | Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread (as a percent)	1.85%