Income Taxes (Reconciliation of U.S Statutory Rate to Effective Tax Rate) (Details)	12 Months Ended			21 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Statutory tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal tax benefit		(0.50%)	0.30%	(2.50%)
Taxes on international activities		(0.10%)	(2.10%)	0.80%
Research credit		(3.10%)	(3.60%)	(4.50%)
Net excess income tax benefit from stock-based compensation		(4.20%)	(2.80%)	(2.50%)
Adjustments of prior period tax items		0.40%	1.00%
Compensation and benefits		0.50%	0.40%	0.30%
Other items, net		1.10%	0.50%	1.50%
Effective tax rate		15.10%	14.70%	14.10%