Retirement and Post-Retirement Employee Benefit Plans Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	$ 15.4	$ 15.8	$ 14.8
Retirement Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	65.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	4.00%
Defined Contribution Plan, Employer Contribution Service Period Until Eligibility	1 year
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%
Defined Contribution Plan, Employer Discretionary Contribution Percent	4.00%
Defined Contribution Plan, Percent of Equity Securities Issued by Employer and Related Parties Included in Plan Assets	3.70%	4.20%
Defined Contribution Plan, Vesting Period	3 years