Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Effective Tax Rate Reconciliation
Statutory tax rate	21.00%	24.50%	35.00%
State and local income taxes	0.10%	1.00%	0.70%
Non-United States taxes	(4.80%)	(4.40%)	(9.30%)
Repatriation of foreign earnings	2.80%	4.20%	0.50%
Foreign-derived intangible income	(1.60%)	0.00%	0.00%
Impact of the Tax Act	0	0.366	0
Foreign currency transaction loss	0.00%	0.00%	(1.90%)
Change in valuation allowance	7.60%	0.70%	0.10%
Share-based compensation	(0.90%)	(1.30%)	(2.80%)
Research and development tax credit	1.20%	1.30%	0.60%
Other	(0.20%)	(0.20%)	(1.30%)
Effective income tax rate	22.80%	59.80%	20.40%
PTC
Effective Tax Rate Reconciliation
Change in valuation allowance	7.50%
Effective income tax rate reconciliation, change in deferred tax assets valuation allowance, amount	$ 67.3