Debt (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2016	Jun. 30, 2016
Long-term Debt Instruments [Line Items]
Letters of Credit Outstanding, Amount	$ 2,698
Deferred Finance Costs, Current, Net	105
Deferred Finance Costs, Noncurrent, Net	373
Revolving Credit Facility [Member]
Long-term Debt Instruments [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	250,000
Line of Credit Facility, Amount Outstanding	11,000	$ 33,000
Letters of Credit Outstanding, Amount	2,726	2,707
Line of Credit Facility, Remaining Borrowing Capacity	$ 236,274	$ 214,293
Debt, Weighted Average Interest Rate	1.63%	1.44%
Minimum [Member] | Revolving Credit Facility [Member]
Long-term Debt Instruments [Line Items]
Line of Credit Facility, Commitment Fee Percentage	0.09%
Maximum [Member] | Revolving Credit Facility [Member]
Long-term Debt Instruments [Line Items]
Line of Credit Facility, Commitment Fee Percentage	0.175%
Long-term Debt [Member]
Long-term Debt Instruments [Line Items]
Debt Instrument, Face Amount	$ 125,000
Long-term Debt	$ 122,656	$ 123,438
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	1.56%	1.50%
Prudential Facility [Domain]
Long-term Debt Instruments [Line Items]
Long-term Debt	$ 170,000
Debt Instrument, Unused Borrowing Capacity, Amount	50,000
Prudential Facility - Series C [Member]
Long-term Debt Instruments [Line Items]
Long-term Debt	$ 120,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.19%
Prudential Facility - Series D [Member]
Long-term Debt Instruments [Line Items]
Long-term Debt	$ 50,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.21%
State of Ohio Assumed Debt [Member]
Long-term Debt Instruments [Line Items]
Debt Instrument, Face Amount	$ 2,359
Long-term Debt	$ 1,840	$ 1,896
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.50%
Adjustments for New Accounting Pronouncement [Member]
Long-term Debt Instruments [Line Items]
Deferred Finance Costs, Current, Net		105
Deferred Finance Costs, Noncurrent, Net		$ 399