Income Taxes - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
	Dec. 22, 2017	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Possible decrease in tax expense in next 12 months		$ 2.0			$ 2.0
Taxes paid on cash distribution		$ 28.0			$ 28.0		$ 22.1
Effective income tax rate		38.50%	40.60%		39.80%	(640.60%)
Increase in income tax expense		$ 22.3			$ 909.1
Impact of changes in US tax legislation		15.3			15.3
Increase in income tax expense of federal rate applied to pretax income		13.3			17.1
Increase from reversal of reserves			$ 1.6			$ 5.2
Decrease in differences in tax filings from provision		4.8			2.6
Decrease in deferred tax assets valuation allowance, amount		$ 1.1			$ 2.1
Income tax benefit from reorganization				$ 876.1		$ 876.1
Adjustment of deferred tax assets and liabilities	$ 15.3
Impact of changes in US tax legislation, as a percent		11.10%			7.60%