Leases - Supplemental Cash Flow Information Related to Company's Leases (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2019 USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 6
Right-of-use assets obtained in exchange for new operating lease liabilities	2
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 20