Debt and Financing Arrangements - Additional Information (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2019 USD ($)
$2.5 billion facility expiring Dec 2024 [Domain]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,500
$500 million facility expiring Dec 2020 [Domain]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 500
$2 billion facility, terminated Dec 2019 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Term	5 years
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,000
Combined $750 million of facilities terminated Dec 2019 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Term	364 days
Line of Credit Facility, Maximum Borrowing Capacity	$ 750
Revolving Credit Facility [Member] | Floating rate term loan [Domain]
Debt Instrument [Line Items]
Debt Instrument, Term