Pension Plans (Details 3) (Pension Plans., USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Post-retirement plan
Fair values of plan assets	$ 574.7	$ 508.8
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	574.7	508.8
Cash and cash equivalents
Post-retirement plan
Fair values of plan assets	4.6	5.3
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	4.6	5.3
Diversified funds
Post-retirement plan
Fair values of plan assets	77.9	69.0
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	77.9	69.0
Equity funds
Post-retirement plan
Fair values of plan assets	181.9	166.3
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	181.9	166.3
Fixed income funds
Post-retirement plan
Fair values of plan assets	226.8	190.0
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	226.8	190.0
Hedge funds
Post-retirement plan
Fair values of plan assets	40.5	34.8
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	40.5	34.8
Assets held by insurance company
Post-retirement plan
Fair values of plan assets	37.5	36.2
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	37.5	36.2
Real estate
Post-retirement plan
Fair values of plan assets	5.5	7.2
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	5.5	7.2
Quoted Prices in Active Markets for Identical Assets (Level 1)
Post-retirement plan
Fair values of plan assets	4.6	29.5
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	4.6	29.5
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Post-retirement plan
Fair values of plan assets	4.6	5.3
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	4.6	5.3
Quoted Prices in Active Markets for Identical Assets (Level 1) | Diversified funds
Post-retirement plan
Fair values of plan assets		24.2
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year		24.2
Quoted Prices in Active Markets for Similar Assets (Level 2)
Post-retirement plan
Fair values of plan assets	559.5	469.3
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	559.5	469.3
Quoted Prices in Active Markets for Similar Assets (Level 2) | Diversified funds
Post-retirement plan
Fair values of plan assets	77.9	44.8
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	77.9	44.8
Quoted Prices in Active Markets for Similar Assets (Level 2) | Equity funds
Post-retirement plan
Fair values of plan assets	181.9	166.3
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	181.9	166.3
Quoted Prices in Active Markets for Similar Assets (Level 2) | Fixed income funds
Post-retirement plan
Fair values of plan assets	226.8	190.0
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	226.8	190.0
Quoted Prices in Active Markets for Similar Assets (Level 2) | Hedge funds
Post-retirement plan
Fair values of plan assets	29.9	24.8
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	29.9	24.8
Quoted Prices in Active Markets for Similar Assets (Level 2) | Assets held by insurance company
Post-retirement plan
Fair values of plan assets	37.5	36.2
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	37.5	36.2
Quoted Prices in Active Markets for Similar Assets (Level 2) | Real estate
Post-retirement plan
Fair values of plan assets	5.5	7.2
Changes in the fair value of Level 3 assets
Fair value of plan assets at end of year	5.5	7.2
Significant Unobservable Inputs (Level 3)
Post-retirement plan
Fair values of plan assets	10.6	10.0
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year	10.0	9.6
Actual return on plan assets, relating to assets still held at reporting date	0.9	(0.8)
Actual return on plan assets, relating to assets sold during the period		0.5
Purchases, sales and settlements	(0.3)	5.2
Transfer into / (out of) Level 3		(4.5)
Fair value of plan assets at end of year	10.6	10.0
Significant Unobservable Inputs (Level 3) | Hedge funds
Post-retirement plan
Fair values of plan assets	10.6	10.0
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year	10.0	5.1
Actual return on plan assets, relating to assets still held at reporting date	0.9	(0.8)
Actual return on plan assets, relating to assets sold during the period		0.5
Purchases, sales and settlements	(0.3)	5.2
Fair value of plan assets at end of year	10.6	10.0
Significant Unobservable Inputs (Level 3) | Other
Changes in the fair value of Level 3 assets
Fair value of plan assets at beginning of year		4.5
Transfer into / (out of) Level 3		$ (4.5)