Employee Benefit Plans - Defined Benefit Pension Plans Weighted-Average Asset Allocations (Detail)	Sep. 30, 2020	Sep. 30, 2019
U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Debt securities	95.00%	68.00%
Cash and other securities	5.00%	32.00%
Total	100.00%	100.00%
Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Equity securities	39.00%	39.00%
Debt securities	50.00%	50.00%
Real estate	6.00%	6.00%
Cash and other securities	5.00%	5.00%
Total	100.00%	100.00%