Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended																12 Months Ended
	Sep. 30, 2015		Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2014	[1]	Sep. 30, 2014		Jun. 30, 2014	[1]	Mar. 31, 2014	[1]	Dec. 31, 2013	[1]	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Recognized settlement losses	$ (7.0)	[1]	$ (1.6)		$ (12.6)		$ 0.0		$ (5.5)	[1]	$ 0.0		$ 0.0		$ 0.0		$ (21.2)	[1]	$ (5.5)	[1]	$ (12.4)
Shares of Common Stock in ESOP	3,402,625																3,402,625
Defined Contribution Plan, Cost Recognized																	$ 44.2		45.2		$ 40.6
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions																	137.5
ABO for all defined benefit pension plans	$ 4,444.8								$ 4,360.0								4,444.8		$ 4,360.0
Pension arrangements not funded because of jurisdictional practice, accumulated benefit obligation	97.7																97.7
Pension arrangements not funded because of jurisdictional practice, projected benefit obligation	$ 101.5																101.5
Pension Plans, Defined Benefit [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for next fiscal year																	100.0
Pension Plans, Defined Benefit [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for next fiscal year																	$ 120.0
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate																	2.60%		2.40%		1.90%
Accumulated postretirement benefit obligation discount rate	2.40%								2.60%								2.40%		2.60%
Net actuarial loss	$ 11.9								$ 15.0								$ 11.9		$ 15.0
Actuarial loss estimated																	$ (0.7)

[1] For additional information, see Note 16, Retirement Benefits.