Income Taxes - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended					9 Months Ended
	Dec. 22, 2017	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Effective tax rates		23.40%		23.70%			25.20%	(147.10%)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Provisional Estimate of Benefit (Expense) Impact on Remeasurement of Deferred Tax Balances				$ (4.1)	$ 31.5	$ 1,174.0
Tax cuts and jobs act, accounting complete			true
Income tax expense from revaluation of deferred tax assets and liabilities			$ 0.4
Additional income tax expense from transition tax provisional liability			$ 3.7