Long-term Debt (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Dec. 31, 2013	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015	Sep. 30, 2014
Debt financing costs			$ 2,359	$ 1,297
Balance of unamortized debt issuance costs	$ 5,834		$ 5,834			$ 4,276
2008 Note Purchase Agreement [Member]
Issuance Date			Oct. 01, 2008
2009 Note Purchase Agreement [Member]
Issuance Date			Apr. 01, 2009
2013 Note Purchase Agreement [Member]
Issuance Date			Oct. 01, 2013
Face Amount	$ 250,000		$ 250,000
Debt financing costs		$ 1,297
Series J Notes [Member]
Variable Rate Basis			LIBOR
Basis Spread On Variable Rate			1.25%
Variable interest rate	1.53%		1.53%
First Closing Notes [Member]
Issuance Date			Oct. 01, 2013
Second Closing Notes [Member]
Issuance Date			Nov. 15, 2013
Foreign Lines of Credit And Overdraft Facilities [Member]
Outstanding borrowings	$ 0		$ 0
Revolving Credit Facility [Member]
Variable Rate Basis			LIBOR
Revolving Credit Facility [Member] | Minimum [Member]
Basis Spread On Variable Rate			0.85%
Revolving Credit Facility [Member] | Maximum [Member]
Basis Spread On Variable Rate			1.65%
Chinese Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	22,700		$ 22,700			22,700
Outstanding borrowings	$ 0		$ 0
Chinese Credit Facility, RMB Denominated Loan [Member]
Variable Rate Basis			interest at the prevailing interest rate offered by the People's Bank of China on the date of borrowing, plus a margin equal to 25% of that prevailing rate
Chinese Credit Facility, USD Denominated Loan [Member]
Variable Rate Basis			interest at the lender's cost of borrowing rate at the date of borrowing, plus 3%
Revolving Credit Agreement [Member]
Line of Credit Facility, Maximum Borrowing Capacity					$ 600,000
Outstanding borrowings						$ 210,000
Credit facility effective interest rate on outstanding borrowing						1.21%
Amended Revolving Credit Agreement [Member]
Variable interest rate	1.24%		1.24%
Debt Covenant, Leverage Ratio, Maximum
Debt Covenant, Minimum Consolidated Net Worth Calculation, Base Value	$ 800,000		$ 800,000
Debt Covenant, Minimum Consolidated Net Worth Calculation, Percentage of Net Income	50.00%		50.00%
Debt Covenant, Minimum Consolidated Net Worth Calculation, Percentage of Net Proceeds of Issuance of Capital Stock	50.00%		50.00%
Debt Covenant, Leverage Ratio During Material Acquisition Period, Maximum
Line of Credit Facility, Initiation Date	Apr. 28, 2015
Line of Credit Facility, Expiration Date			Apr. 28, 2020
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,000,000		$ 1,000,000
Outstanding borrowings	$ 375,000		$ 375,000
Credit facility effective interest rate on outstanding borrowing	1.24%		1.24%
Amended Revolving Credit Agreement [Member] | Minimum [Member]
Basis Spread On Variable Rate			0.85%
Amended Revolving Credit Agreement [Member] | Maximum [Member]
Basis Spread On Variable Rate			1.65%