Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
Dec. 31, 2011	Jun. 30, 2012 Pension Benefits [Member]	Jun. 30, 2011 Pension Benefits [Member]	Jun. 30, 2012 Pension Benefits [Member]	Jun. 30, 2011 Pension Benefits [Member]	Jun. 30, 2012 Other Postretirement Benefits [Member]	Jun. 30, 2011 Other Postretirement Benefits [Member]	Jun. 30, 2012 Other Postretirement Benefits [Member]	Jun. 30, 2011 Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost		$ 17.8	$ 17.8	$ 53.8	$ 52.9	$ 0.6	$ 0.8	$ 1.7	$ 2.6
Interest cost		41.7	41.6	125.6	123.5	1.8	2.5	5.4	7.6
Expected return on plan assets		(56.8)	(52.2)	(171.0)	(154.3)
Amortization:
Prior service credit		(0.6)	(0.5)	(1.8)	(1.5)	(2.6)	(2.6)	(7.9)	(7.9)
Net actuarial loss		23.6	16.0	71.0	47.8	0.6	1.7	1.8	4.9
Net periodic benefit cost		25.7	22.7	77.6	68.4	0.4	2.4	1.0	7.2
Retirement Benefits (Textual) [Abstract]
Voluntary Contribution To Qualified Pension Plan Trust	$ 300

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The amount of contributions made by the employer in excess of statutory requirements.

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The amount of gains or losses recognized in net periodic benefit cost.

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The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

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An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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