Summary of Significant Accounting Policies - Schedule of Impact of Adoption on Consolidated Statement of Cash Flows (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net income	$ 67	$ (1)	$ 153	$ 4
Deferred income taxes			27	38
Changes in operating assets and liabilities:
Accounts receivable			(90)	(15)
Accounts payable and accrued liabilities			(100)	(100)
Royalty payables			46	68
Deferred revenue			(19)	(16)
Other balance sheet changes			28	(10)
Net cash provided by operating activities			99	136
Effect of exchange rate changes on cash and equivalents			(1)	6
Net decrease in cash and equivalents			(44)	(35)
Cash and equivalents at beginning of period			514	647
Cash and equivalents at end of period	470	$ 612	470	$ 612
Balances Without Adoption Of ASC 606 | Topic 606
Cash flows from operating activities
Net income	69		145
Deferred income taxes			22
Changes in operating assets and liabilities:
Accounts receivable			(63)
Accounts payable and accrued liabilities			(103)
Royalty payables			30
Deferred revenue			(17)
Other balance sheet changes			31
Net cash provided by operating activities			99
Effect of exchange rate changes on cash and equivalents			(1)
Net decrease in cash and equivalents			(44)
Cash and equivalents at beginning of period			514
Cash and equivalents at end of period	470		470
Impact of Adoption | Topic 606
Cash flows from operating activities
Net income	$ (2)		8
Deferred income taxes			5
Changes in operating assets and liabilities:
Accounts receivable			(27)
Accounts payable and accrued liabilities			3
Royalty payables			16
Deferred revenue			(2)
Other balance sheet changes			$ (3)