Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value (Details) - Recurring - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Other noncurrent assets
Total assets at fair value	$ 53	$ 77
Accrued expenses and other liabilities
Total liabilities at fair value	1	1
Level 1
Other noncurrent assets
Non-qualified trust funds	25	30
Level 2
Prepaid expenses and other current assets
Currency derivatives	1	1
Accrued expenses and other liabilities
Currency derivatives	1	1
Money market funds | Level 1
Cash and cash equivalents
Cash and cash equivalents	5	11
Time deposits | Level 2
Cash and cash equivalents
Cash and cash equivalents	$ 22	$ 35