Pension Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net Periodic Benefit Cost Abstract
Interest cost	$ 10	$ 9	$ 29	$ 26
Expected return on plan assets	(10)	(10)	(30)	(30)
Recognized actuarial loss	1	1	4	5
Net periodic benefit cost	$ 1	$ 0	$ 3	$ 1