Income Taxes - Effective Rate Reconciliation (Details)	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Federal statutory rate effect of:	21.00%	21.00%	21.00%
U.S. State and local income taxes	1.00%	1.80%	1.20%
Foreign earnings and losses taxed at different rates	1.10%	1.00%	0.90%
Change in valuation allowance	0.90%	1.90%	1.00%
U.K. bank tax	0.026	0.004	0
U.S. permanent items	0.002	(0.012)	0.006
Non-deductible compensation	0.70%	1.90%	0.60%
Foreign permanent items	(2.80%)	(2.30%)	0.30%
U.S. bargain purchase gain	0.00%	(0.50%)	(8.30%)
GILTI	0.60%	0.60%	0.70%
Effective rate	25.30%	24.60%	18.00%