Income Taxes - Additional information (Detail) - USD ($) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2017	Aug. 31, 2018	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Operating Loss Carryforwards [Line Items]
Statutory federal corporate tax rate	35.00%	21.00%		25.70%	35.00%	35.00%
Tax benefit due to remeasurement of deferred tax assets and liabilities				$ 33.6
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense				6.9
Income tax and earnings from unconsolidated affiliates,Domestic u.s. operations				110.8	$ 123.2	$ 264.8
Income tax and earnings from unconsolidated affiliates,Foreign operations				112.8	113.0	$ 130.3
Net increase (Decrease) in the valuation allowance				0.1
Unrecognized tax benefits, excluding interest		$ 1.6		1.6	1.8
Accrued interest related to uncertain tax provisions		0.2		0.2
Interest benefit relating to reserves for uncertain tax provisions				$ 0.2	$ 0.2
Maximum
Operating Loss Carryforwards [Line Items]
Transition tax payable period				8 years
Scenario Forecast
Operating Loss Carryforwards [Line Items]
Statutory federal corporate tax rate			21.00%
State
Operating Loss Carryforwards [Line Items]
Credit carryforwards		1.5		$ 1.5
Credit carryforwards expiration Year				2021
Foreign
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		$ 8.5		$ 8.5
Operating loss carryforwards expiration dates				2020