Pension Benefit Obligations - Asset Changes (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Change in plan assets
Fair value of plan assets at beginning of year	$ 1,421.4
Fair value of plan assets at end of year	1,527.9	$ 1,421.4
United States
Change in plan assets
Fair value of plan assets at beginning of year	455.5	470.4	$ 456.9
Actual return on plan assets	26.2	11.1	39.0
Employer contributions	14.5	11.6	12.3
Participant contributions	0.2	0.2	0.1
Benefits and expenses paid	(36.0)	(37.8)	(37.9)
Plan settlements	(1.3)
Fair value of plan assets at end of year	459.1	455.5	470.4
International
Change in plan assets
Fair value of plan assets at beginning of year	965.9	993.1	973.2
Actual return on plan assets	180.3	29.3	9.6
Employer contributions	28.1	27.8	25.8
Participant contributions	0.3	0.4	0.4
Benefits and expenses paid	(41.2)	(53.7)	(48.3)
Plan settlements	(3.7)	(3.0)
Foreign currency translation gain (loss)	(60.9)	(28.0)	32.4
Fair value of plan assets at end of year	$ 1,068.8	$ 965.9	$ 993.1

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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- Definition

Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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- Definition

Amount of contributions received by defined benefit plan from participant which increase benefit obligation.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) plan assets of defined benefit plan.

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Amount of payment, which decreases plan assets of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract.

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