Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Other noncurrent assets
Total assets at fair value	$ 60	$ 53
Accrued expenses and other liabilities
Total liabilities at fair value	2	1
Level 1
Other noncurrent assets
Non-qualified trust funds	21	25
Level 1 | Money market funds
Cash and cash equivalents
Cash and cash equivalents	3	5
Level 2
Prepaid expenses and other current assets
Currency derivatives	1	1
Accrued expenses and other liabilities
Currency derivatives	2	1
Level 2 | Time deposits
Cash and cash equivalents
Cash and cash equivalents	34	22
Prepaid expenses and other current assets
Time deposits	$ 1	$ 0