Derivative Instruments and Hedging Activities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Mar. 31, 2017	Sep. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Amount of net losses associated with interest rate hedges to be reclassified with interest rate hedges during the next 12 months			$ 3.5
Amount of net gains associated with currency rate risk to be reclassified into earnings during the next 12 months			9.4
Restricted cash in brokerage accounts	$ 40.0	$ 40.0	$ 0.3	$ 15.6
Loss on ineffectiveness and excluded derivatives recognized in income	$ 2.1	$ 5.5