Credit Arrangements - Note Purchase Agreement (Details) (USD $)	3 Months Ended				0 Months Ended		0 Months Ended
	Mar. 31, 2011	Jun. 30, 2014	Jun. 30, 2013	Mar. 22, 2013	Jul. 25, 2013 Senior Notes [Member] 3.11% Senior Notes due in 2020 [Member]	Jun. 30, 2014 Senior Notes [Member] 3.11% Senior Notes due in 2020 [Member]	Jul. 25, 2013 Revolving Credit Facility [Member] 2013 Credit Agreement [Member]	May 31, 2013 Treasury Lock [Member]	May 31, 2013 Treasury Lock 1 [Member] Treasury Lock [Member]	May 31, 2013 Treasury Lock 2 [Member] Treasury Lock [Member]	May 31, 2013 Treasury Lock 3 [Member] Treasury Lock [Member]
Debt Instrument [Line Items]
Principal amount of debt					$ 100,000,000
Interest rate					3.11%
Proceeds from Issuance of Long-term Debt	107,500,000				100,000,000
Repayments of Long-term Lines of Credit							100,000,000
Prepayment of aggregate principal amount, minimum percent					10.00%
Long-term Line of Credit				400,000,000		100,000,000
Deferred Finance Costs, Net						400,000
Number of treasury lock agreements								3
Notional Amount		$ 568,853,000	$ 509,947,000						$ 25,000,000	$ 25,000,000	$ 25,000,000
Debt, Weighted Average Interest Rate		1.60%