Retirement and Other Benefit Plans - Schedule Of Reconciliation Of Fair Value Of Plan Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Retirement and Other Benefit Plans
Fair value of plan assets at beginning of year		$ 77.2	$ 73.3
Actual return on plan assets		3.6	5.9
Employer contributions	$ 25.7	26.4	2.7
Gross benefits paid		(4.8)	(4.7)
Settlements		(102.4)	0.0
Fair value of plan assets at end of year	$ 0.0	$ 0.0	$ 77.2

No definition available.

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- Definition

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

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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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Amount of (increase) decrease to benefit obligation of defined benefit plan from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Includes, but is not limited to, lump-sum cash payment to participant in exchange for right to receive specified benefits, purchase of nonparticipating annuity contract and change from remeasurement.

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