Financial Instruments (Schedule of Interest Rate Swaps and Cross Currency Interest Rate Swaps) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Sep. 30, 2016
Interest Rate Swaps Contracts [Member] | Fair Value Hedges [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
US$ Notional	$ 600.0	$ 600.0
Average Pay %	LIBOR	LIBOR
Average Receive %	2.28%	2.28%
Years Average Maturity	1 year 10 months	2 years 4 months
Cross Currency Interest Rate Swaps [Member] | Hedges Not Designated [Member]
Derivative [Line Items]
US$ Notional	$ 41.7	$ 27.4
Average Pay %	3.40%	3.62%
Average Receive %	1.78%	0.81%
Years Average Maturity	1 year 11 months	1 year 10 months
Cross Currency Interest Rate Swaps [Member] | Net Investment Hedges [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
US$ Notional	$ 503.4	$ 517.7
Average Pay %	3.24%	3.24%
Average Receive %	2.39%	2.43%
Years Average Maturity	2 years	2 years 7 months
Cross Currency Interest Rate Swaps [Member] | Cash Flow Hedges [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
US$ Notional	$ 1,088.9	$ 1,088.9
Average Pay %	4.77%	4.77%
Average Receive %	2.72%	2.72%
Years Average Maturity	2 years 10 months	3 years 4 months