Pension and Other Post-Retirement Benefits - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to 401(k) Plan, percentage of employee contributions	50.00%
Employer contributions to 401(k) Plan, percentage of eligible salary	6.00%
Total contributions to 401(k) Plan	$ 8.1	$ 6.7	$ 6.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (0.1)	(0.3)	$ 0.4
Document Period End Date	Sep. 30, 2019
Defined Benefit Plan, Benefit Obligation	$ 39.9	34.7
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (16.8)	$ (11.1)