Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Other noncurrent assets
Total assets at fair value	$ 84	$ 79
Accrued expenses and other liabilities
Total liabilities at fair value	1	0
Level 1
Other noncurrent assets
Non-qualified trust funds	20	20
Level 1 | Money market funds
Cash and cash equivalents
Cash and cash equivalents	1	0
Level 2
Prepaid expenses and other current assets
Currency derivatives	1	0
Accrued expenses and other liabilities
Currency derivatives	1	0
Level 2 | Time deposits
Cash and cash equivalents
Cash and cash equivalents	$ 62	$ 59