Retirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Postemployment Benefits, Period Expense	$ 0.1	$ 0.1	$ 0.2	$ 0.2
Defined Contribution Plan, Cost Recognized	$ 2.3	$ 2.4	$ 4.6	$ 4.5