Pension Benefit Obligations - Level 3 (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year	$ 1,295.8
Fair value of plan assets at end of year	1,390.7	$ 1,295.8
Level 3
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year	3.4	26.8
Actual return on plan assets, relating to assets still held at reporting date	0.4	(0.2)
Actual return on plan assets, relating to assets sold during the period		(2.1)
Purchases, sales and settlements	0.2	(25.4)
Transfer into / (out of) Level 3		3.2
Change due to exchange rate changes		1.1
Fair value of plan assets at end of year	$ 4.0	$ 3.4

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets sold.

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

+ References

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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.

+ References

No definition available.

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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.

+ References

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- Definition

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

+ References

+ Details

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- Definition

Amount, measured using unobservable input, of increase (decrease) in plan asset of defined benefit plan from purchase, sale and settlement of trade associated with underlying investment.

+ References

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs.

+ References

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