Contingencies - Additional Information (Detail) $ in Millions	5 Months Ended
	Jul. 31, 2018 Claim	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Number of arbitration claims filed | Claim	325
Other Accrued Expenses [Member]
Loss Contingencies [Line Items]
Accrual for legal fees and settlements | $		$ 0.9	$ 8.7