Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Decrease in valuation allowance					$ 45.6
Benefit related to re-measurement of deferred tax liabilities					0.7
U.S. statutory federal tax rate (as a percent)	21.00%		35.00%	21.00%
Reductions in unrecognized tax benefits from expiration						$ 0.9
Cumulative effect adjustment to retained earnings					$ 4.0
Toll charge, payable period					8 years
Toll charge, estimated foreign earnings		$ 120.0		$ 120.0	$ 120.0
Toll charge, estimated foreign earnings, provision amount, unrecorded					$ 5.2
U.S. statutory federal tax rate, prorated allocation (as a percent)		24.50%			24.50%
Anticipated unrecognized tax benefit reduction during next twelve months		$ 0.2		$ 0.2	$ 0.2