Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended																12 Months Ended
	Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2014	[1]	Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	$ 2.8		$ 1.0		$ 2.6		$ 0.0		$ 7.0		$ 1.6		$ 12.6		$ 0.0		$ 6.4	[1]	$ 21.2	[1]	$ 5.5
US [Member]
Retirement Benefits [Abstract]
Defined Benefit Plan Recognized Gain Loss Due to Curtailments																	0.0		(5.3)		0.0
Defined Benefit Plan Disclosure [Line Items]
Service cost																	36.5		42.2		42.6
Interest cost																	110.7		124.7		130.7
Expected return on plan assets																	(202.0)		(202.0)		(187.8)
Actuarial loss amortization																	85.3		78.9		78.3
Prior service cost amortization																	2.8		2.8		2.9
Settlement loss																	5.1		18.9		4.8
Curtailments																	0.0		5.3		0.0
Special termination benefits																	2.0		7.2		0.2
Other																	(0.3)		1.0		0.0
Net periodic benefit cost																	40.1		79.0		71.7
International [Member]
Retirement Benefits [Abstract]
Defined Benefit Plan Recognized Gain Loss Due to Curtailments																	1.1		0.0		0.0
Defined Benefit Plan Disclosure [Line Items]
Service cost																	24.3		31.3		36.0
Interest cost																	44.3		57.8		67.2
Expected return on plan assets																	(78.3)		(79.8)		(78.1)
Actuarial loss amortization																	35.6		41.4		36.1
Prior service cost amortization																	(0.2)		0.0		0.2
Settlement loss																	1.3		2.3		0.7
Curtailments																	(1.1)		0.0		0.0
Special termination benefits																	0.0		1.5		0.1
Other																	2.1		2.1		2.0
Net periodic benefit cost																	28.0		56.6		64.2
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost																	2.2		2.8		3.3
Interest cost																	2.0		2.2		2.3
Actuarial loss amortization																	0.7		0.8		1.7
Net periodic benefit cost																	$ 4.9		$ 5.8		$ 7.3

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