Credit Agreements (Details) $ in Thousands, € in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	May 31, 2013 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 EUR (€)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 EUR (€)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 11, 2016 USD ($)	Oct. 01, 2015	Sep. 30, 2015 USD ($)	Jun. 12, 2015 USD ($)	Jul. 25, 2013	Sep. 30, 2011
Line of Credit Facility [Line Items]
Derivative, Notional Amount					$ 702,500			$ 468,700
Letters of Credit Outstanding, Amount					10,200
Long-term Debt, Gross					780,800							$ 7,100
Interest rate swap, fixed interest rate	0.73%									1.104%
JP Morgan [Member]
Line of Credit Facility [Line Items]
Transfers of Financial Assets Including Debt Activity			$ 700
Other Short-term Borrowings											$ 0
HSBC [Member]
Line of Credit Facility [Line Items]
Investment Interest Rate Range End			2.00%
Credit agreement maximum borrowing capacity | €				€ 100.0
Investment Interest Rate Range Start			1.00%
Remaining borrowing available under revolving credit facility | €				100.0
JP Morgan UK [Member]
Line of Credit Facility [Line Items]
Credit agreement maximum borrowing capacity							$ 4,500
Remaining borrowing available under revolving credit facility							$ 4,500
ING Bank NV [Member]
Line of Credit Facility [Line Items]
Credit agreement maximum borrowing capacity | €				€ 7.5
Minimum [Member] | JPMorganLOC [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate During Period		2.00%
Maximum [Member] | JPMorganLOC [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate During Period		4.00%
Senior Notes due in 2020 [Member]
Line of Credit Facility [Line Items]
Deferred Finance Costs, Noncurrent, Net											200
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Remaining borrowing available under revolving credit facility					165,000
Interest Rate Swap [Member]
Line of Credit Facility [Line Items]
Interest rate swap, fixed interest rate														1.30%
Principal amount of debt hedged with an interest rate swap agreement	$ 100,000	$ 100,000
Uncommitted Overdraft Facility [Member] | Unsecured Debt [Member] | ING Bank NV [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Unused Borrowing Capacity, Amount | €						€ 7.5
Uncommitted Overdraft Facility [Member] | Unsecured Debt [Member] | Minimum [Member] | ING Bank NV [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage								2.00%
Uncommitted Overdraft Facility [Member] | Unsecured Debt [Member] | Maximum [Member] | ING Bank NV [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage								4.00%
2016 Credit Agreement [Member]
Line of Credit Facility [Line Items]
Long-term Debt					285,000
Max commitment fee on revolving loan unused amount, percentage		0.25%
2016 Credit Agreement [Member] | Swingline Loan [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity									$ 0
2016 Credit Agreement [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity									0
Line of credit facility amount outstanding									0
2016 Credit Agreement [Member] | Term Loan [Member]
Line of Credit Facility [Line Items]
Long-term Debt					392,500				$ 0
Senior Notes due in 2020 [Member] | Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage													3.11%
Long-term Debt, Gross											$ 100,000
Designated as Hedging Instrument [Member]
Line of Credit Facility [Line Items]
Derivative, Notional Amount					$ 355,700			$ 384,500