Pension and Defined Contribution Plans - Fair Value Measurements and Benefit Payments (Details) $ in Millions	12 Months Ended
	Aug. 31, 2019 USD ($) multiemployer_plan	Aug. 31, 2018 USD ($)	Aug. 31, 2017 USD ($)
Multiemployer Defined Pension Plans
Multiemployer Pension Plans [Abstract]
Number of multi-employer plans | multiemployer_plan	2
Contributions to Multi-employer Pension Plans	$ 0.5	$ 0.5	$ 0.5
Defined Contribution Plan
Defined Contribution Plan [Abstract]
Defined contribution plan, cost recognized	8.1	8.0	8.0
Common stock included in defined contribution plan, market value	$ 7.4
Common stock included in defined contribution plan as percentage of total fair value of assets in plan	2.00%
Domestic Plans | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	$ 151.5	149.4	136.8
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2020	9.5
2021	9.3
2022	12.5
2023	24.2
2024	17.8
2025-2029	66.8
Domestic Plans | Pension Plan | Level 1 | Mutual Funds: Domestic large cap equity fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	45.6	48.3
Domestic Plans | Pension Plan | Level 1 | Mutual Funds: Foreign equity fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	20.5	20.8
Domestic Plans | Pension Plan | Level 1 | Collective trust: Domestic small cap equities
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
Domestic Plans | Pension Plan | Level 1 | Short-term fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	6.0	7.6
Domestic Plans | Pension Plan | Level 2 | Mutual Funds: Domestic large cap equity fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
Domestic Plans | Pension Plan | Level 2 | Mutual Funds: Foreign equity fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
Domestic Plans | Pension Plan | Level 2 | Collective trust: Domestic small cap equities
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	14.6	16.8
Domestic Plans | Pension Plan | Level 2 | Short-term fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
Domestic Plans | Pension Plan | Level 3 | Mutual Funds: Domestic large cap equity fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
Domestic Plans | Pension Plan | Level 3 | Mutual Funds: Foreign equity fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
Domestic Plans | Pension Plan | Level 3 | Collective trust: Domestic small cap equities
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
Domestic Plans | Pension Plan | Level 3 | Short-term fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
Domestic Plans | Pension Plan | Level 1,2 and 3
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	86.7	93.5
Domestic Plans | Pension Plan | Level 1,2 and 3 | Mutual Funds: Domestic large cap equity fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	45.6	48.3
Domestic Plans | Pension Plan | Level 1,2 and 3 | Mutual Funds: Foreign equity fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	20.5	20.8
Domestic Plans | Pension Plan | Level 1,2 and 3 | Collective trust: Domestic small cap equities
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	14.6	16.8
Domestic Plans | Pension Plan | Level 1,2 and 3 | Short-term fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	6.0	7.6
Domestic Plans | Pension Plan | NAV
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	64.8	55.9
Domestic Plans | Pension Plan | NAV | Fixed-income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	57.4	48.9
Domestic Plans | Pension Plan | NAV | Real estate fund
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	7.4	7.0
International Plans | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	30.7	30.9	$ 34.1
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2020	1.0
2021	1.0
2022	1.0
2023	1.1
2024	1.1
2025-2029	6.3
International Plans | Pension Plan | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	22.4	19.1
International Plans | Pension Plan | Short-term fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.3	0.3
International Plans | Pension Plan | Multi-strategy investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	3.0	3.9
International Plans | Pension Plan | Fixed-income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	5.0	7.6
International Plans | Pension Plan | Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
International Plans | Pension Plan | Level 1 | Short-term fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.3	0.3
International Plans | Pension Plan | Level 1 | Multi-strategy investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
International Plans | Pension Plan | Level 1 | Fixed-income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
International Plans | Pension Plan | Level 2 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	22.4	19.1
International Plans | Pension Plan | Level 2 | Short-term fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
International Plans | Pension Plan | Level 2 | Multi-strategy investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	3.0	3.9
International Plans | Pension Plan | Level 2 | Fixed-income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	5.0	7.6
International Plans | Pension Plan | Level 3 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
International Plans | Pension Plan | Level 3 | Short-term fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
International Plans | Pension Plan | Level 3 | Multi-strategy investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	0.0
International Plans | Pension Plan | Level 3 | Fixed-income investments
Defined Benefit Plan Disclosure [Line Items]
Total assets at fair value	0.0	$ 0.0
Qualified Plan | Domestic Plans | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Employer expected contribution to defined benefit plans in next fiscal year	3.6
Qualified Plan | International Plans | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Employer expected contribution to defined benefit plans in next fiscal year	$ 1.0