Derivative Instruments and Hedging Activities (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	May 31, 2018 USD ($) loan	Sep. 23, 2016 EUR (€)
Total Accumulated Other Comprehensive (Loss) Earnings [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Remaining unrecognzied gains (losses) associated with derivative instruments included in AOCI	$ 33,394		$ 33,394		$ (5,004)
Fixed-Rate Cross Currency Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Derivatives in Cash Flow Hedging Relationships [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, number of instruments | loan						5
Derivative, notional amount						$ 400,000
Fixed-Rate Cross Currency Interest Rate Contract [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount						400,000
Floating-Rate Cross Currency Interest Rate Contract [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount						$ 167,420
2016 Note Purchase Agreements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Issuance date			Sep. 23, 2016
Face amount | €							€ 160,000,000
Series M Notes [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	$ 650	$ 925	$ (395)	$ 1,574
Face amount | €							€ 40,000,000