Debt Textuals (Details) - USD ($)	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		$ 19,500,000
Letters of Credit Outstanding, Amount	$ 2,698,000
Debt Issuance Costs, Gross, Current	551,000	105,000
Debt Issuance Cost, Gross, Noncurrent	1,807,000	294,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility unsecured borrowings amount	250,000,000
Letters of Credit Outstanding, Amount	3,625,000	2,441,000
Line of Credit Facility, Remaining Borrowing Capacity	$ 226,875,000	247,559,000
Debt, Weighted Average Interest Rate	3.93%
Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Fees on credit facility	0.10%
Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Fees on credit facility	0.20%
Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 780,000,000
Long-term Debt	$ 775,125,000	$ 120,313,000
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	4.13%	2.25%
Prudential Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 170,000,000
Debt Instrument, Unused Borrowing Capacity, Amount	50,000,000
Prudential Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Fee Amount	0.0025
Prudential Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Fee Amount	0.0125
Prudential Facility - Series C [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 120,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.19%
Prudential Facility - Series D [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 50,000,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.21%
State of Ohio Assumed Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 2,359,000
Long-term Debt	$ 1,438,000	$ 1,669,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.50%