Income Tax Reform - Summary of Tax Cuts and Jobs Act of 2017 Effects (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended	9 Months Ended
Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Reduction in net deferred tax liabilities in the U.S. from the reduction of the U.S. tax rate	$ 0.8	$ 180.3	$ 181.1
Establishment of valuation allowances related to deferred tax assets impacted by TCJA	0.0	(7.6)	(7.6)
Toll-tax on un-repatriated earnings	0.0	(1.4)	(1.4)
Total discrete deferred income tax adjustments	$ 0.8	$ 171.3	$ 172.1
Basic earnings per share (USD per share)	$ 0.00	$ 0.99	$ 0.99
Diluted earnings per share (USD per share)	$ 0.00	$ 0.97	$ 0.97

Change In Income Tax Rate, Effect Of Change On Earnings Per Share, Basic

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Change In Income Tax Rate, Effect of Change on Earnings Per Share, Diluted

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Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense (Benefit)

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