Derivative Instruments and Hedging Activities (Narrative) (Details) € in Thousands, ¥ in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 CNY (¥)	Sep. 30, 2017 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Accumulated OCI on Derivative | $	$ 0	$ 0
Net unrecognized gains on terminated derivative instruments expected to be reclassified to earnings | $	$ 72
Term of gain or loss recognition in interest expense on terminated derivatives recorded in OCI	12 months
Face Amount | €			€ 160,000
EUR Denominated Loan [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on foreign currency transaction designated as a hedge of a net investment in a foreign subsidiary | $	$ 743	2,814
Intercompany Loan [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on foreign currency transaction designated as a hedge of a net investment in a foreign subsidiary | $		$ 1,016
Value of Net Investment Hedging Instruments Used | ¥					¥ 160,000
Total Accumulated Other Comprehensive (Loss) Earnings [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrecognized gains (loss) | $				$ 200		$ 218
Series D Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Issuance Date	Oct. 01, 2008
Series F Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Issuance Date	Apr. 01, 2009
2013 Note Purchase Agreement [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Issuance Date	Oct. 01, 2013
Face Amount | $				$ 250,000
First Closing Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Issuance Date	Oct. 01, 2013
Second Closing Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Issuance Date	Nov. 15, 2013
2016 Note Purchase Agreements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Issuance Date	Sep. 23, 2016
Face Amount | €			160,000
Series M Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Value of Net Investment Hedging Instruments Used | €			40,000
Face Amount | €			40,000
Series N Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Face Amount | €			77,000
Series O Notes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Face Amount | €			€ 43,000