XML 98 R83.htm IDEA: XBRL DOCUMENT v3.20.4
Income Taxes - Effective Income Tax Rate Varied from Statutory Guernsey Tax Rate (Detail)
12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Schedule of Effective Income Tax Rate Reconciliation [Line Items]      
Foreign taxes (percentage) 14.70% 15.60% 15.90%
Effective income tax rate 14.70% 15.60% 15.90%
GUERNSEY      
Schedule of Effective Income Tax Rate Reconciliation [Line Items]      
Statutory Guernsey tax rate 0.00% 0.00% 0.00%