Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Allowance for doubtful accounts
Valuation and Qualifying Account
Balance at beginning of year	$ 27.3	$ 29.7	$ 39.1
Charged (credited) to costs and expenses	30.7	21.7	31.6
Balance at end of year	26.9	27.3	29.7
Uncollectible accounts written off, net of recoveries
Valuation and Qualifying Account
Other	(31.1)	(24.1)	(39.6)
Effects of currency exchange
Valuation and Qualifying Account
Other			(1.4)
Deferred tax assets valuation allowance
Valuation and Qualifying Account
Balance at beginning of year	114.3	131.3	59.2
Charged (credited) to costs and expenses	(7.6)	(5.8)	5.1
Balance at end of year	107.1	114.3	131.3
Foreign tax credit valuation allowance adjustment
Valuation and Qualifying Account
Other	$ 0.4	(8.8)	66.1
Decrease in unusable foreign operating loss carryforwards
Valuation and Qualifying Account
Other		$ (2.4)	(2.6)
Acquisitions
Valuation and Qualifying Account
Other			$ 3.5