Credit Arrangements - Note Purchase Agreement (Details) $ in Thousands	Jul. 25, 2013 USD ($)	Jun. 30, 2015 USD ($)	Jun. 12, 2015 USD ($)	Jun. 30, 2014 USD ($)	May. 31, 2013 USD ($)
Debt Instrument [Line Items]
Long-term Line of Credit			$ 7,100
Notional Amount		$ 468,480		$ 568,853
Senior Notes [Member] | 3.11% Senior Notes due in 2020 [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 100,000
Interest rate	3.11%
Proceeds from Issuance of Long-term Debt	$ 100,000
Prepayment of aggregate principal amount, minimum percent	10.00%
Long-term Line of Credit		100,000
Deferred Finance Costs, Net		$ 300
Revolving Credit Facility [Member] | 2013 Credit Agreement [Member]
Debt Instrument [Line Items]
Repayments of Long-term Lines of Credit	$ 100,000
Treasury Lock [Member]
Debt Instrument [Line Items]
Number of treasury lock agreements					3
Treasury Lock 1 [Member] | Treasury Lock [Member]
Debt Instrument [Line Items]
Notional Amount					$ 25,000
Treasury Lock 2 [Member] | Treasury Lock [Member]
Debt Instrument [Line Items]
Notional Amount					25,000
Treasury Lock 3 [Member] | Treasury Lock [Member]
Debt Instrument [Line Items]
Notional Amount					$ 25,000