Commitments and Contingencies - Schedule of Liabilities for Future Environmental Costs (Detail) $ in Millions	Sep. 30, 2016 USD ($)
Loss Contingencies [Line Items]
2017	$ 1.6
2018	1.0
2019	1.0
2020	0.7
2021	1.2
Thereafter	3.8
Total costs	9.3
Less imputed interest	1.2
Reserve amount	8.1
Recurring Costs
Loss Contingencies [Line Items]
2017	0.4
2018	0.5
2019	0.4
2020	0.4
2021	0.5
Thereafter	2.8
Total costs	5.0
Non-Recurring Costs
Loss Contingencies [Line Items]
2017	1.2
2018	0.5
2019	0.6
2020	0.3
2021	0.7
Thereafter	1.0
Total costs	$ 4.3