Retirement Plans - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Withdrawal Obligation	$ 240.5			$ 240.5		$ 247.8
Periods of Payments Used to Calculate Withdrawal Liability in Connection with PIUMPF Withdrawal			20 years
Amount of reduction to previously recorded MEPP withdrawal liability	1.7
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions by employer to pension and supplemental retirement plans	6.6	$ 10.8		16.1	$ 31.5
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions by employer to pension and supplemental retirement plans	$ 2.2	2.3		$ 6.6	7.1
Pace Industry Union Management Pension Fund [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Withdrawal Obligation			$ 180.0
Central States, Southeast and Southwest Areas Pension Fund [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer Plans, Withdrawal Obligation		$ 4.2			$ 4.2