Credit Arrangements - Note Purchase Agreement (Details) $ in Millions	Jul. 25, 2013 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 12, 2015 USD ($)	May 31, 2013 USD ($)
Debt Instrument [Line Items]
Long-term Line of Credit				$ 7.1
Notional Amount		$ 468.7	$ 468.5
Senior Notes [Member] | 3.11% Senior Notes due in 2020 [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 100.0
Interest rate	3.11%
Proceeds from Issuance of Long-term Debt	$ 100.0
Prepayment of aggregate principal amount, minimum percent	10.00%
Long-term Line of Credit		100.0
Deferred Finance Costs, Net		$ 0.2
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		3.05%
Revolving Credit Facility [Member] | 2013 Credit Agreement [Member]
Debt Instrument [Line Items]
Repayments of Long-term Lines of Credit	$ 100.0
Treasury Lock [Member]
Debt Instrument [Line Items]
Number of treasury lock agreements					3
Notional Amount					$ 25.0