Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan, Fair Value of Plan Assets	$ 36.4	$ 33.7
Defined Benefit Plan, Benefit Obligation	$ 36.5	$ 38.5
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.80%	3.60%
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	$ 0.1	$ 4.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 0.3	0.2	$ 0.1
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	6.00%
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 2.0	1.8
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	2.1
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	2.1
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	2.0
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	2.0
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	1.9
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	9.5
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 6.1	$ 5.3	$ 5.1
Debt Securities [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	80.00%
Equity Securities [Member]
Defined Benefit Plan, Actual Plan Asset Allocations	20.00%
UK Plan [Member]
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	100.00%
UK Plan [Member] | Maximum [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent	10.00%
401k Plan [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent	62.50%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	8.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage, Two to Three Years	33.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage, Three to Four Years	66.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage, All Years	100.00%
401k Plan [Member] | Maximum [Member]
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	80.00%
401k Plan [Member] | Minimum [Member]
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	1.00%