Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Company contributions	$ 51.8	$ 76.4	$ 137.5
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	100.0
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	120.0
Change in Assumptions for Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated impact of change in accounting estimate on net periodic benefit cost in the current fiscal year	(30.0)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Recognized settlement losses	$ 0.0	$ 0.0