Debt and Borrowings (Narrative) (Details)		3 Months Ended
	Dec. 12, 2014 USD ($)	Sep. 30, 2017 GBP (£)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 EUR (€)
Line of Credit Facility [Line Items]
Line of credit potential incremental borrowing capacity post-amendment	$ 350,000,000
Revolving credit facility expiration date	Dec. 12, 2019
Interest Coverage Ratio	4.00
Leverage ratio	3.50
Consolidated leverage ratio	4.0
Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving credit facility	$ 1,000,000,000
Borrowings outstanding under credit agreement			$ 739,678,000
Available borrowing capacity			$ 254,142,000
Weighted average interest rate		2.88%	2.88%	2.88%
Credit Agreement [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Commitment fee percentage		0.20%
Credit Agreement [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Commitment fee percentage		0.30%
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Borrowings outstanding under credit agreement			$ 6,180,000
Eurocurrency Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.875%
Eurocurrency Rate [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.70%
Base Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.00%
Base Rate [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.70%
Tilda short-term borrowing arrangements [Member]
Line of Credit Facility [Line Items]
Revolving credit facility | £		£ 52,000,000
Debt term		6 months
Short-term debt, weighted average interest rate		2.72%	2.72%	2.72%
Mona [Member]
Line of Credit Facility [Line Items]
Revolving credit facility | €				€ 12,500,000
Basis spread on variable rate		1.10%
Short-term debt, weighted average interest rate		1.10%	1.10%	1.10%