Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		15 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Income Tax [Line Items]
Payroll tax deferral from CARES Act through December 2020					$ 73
Income taxes	$ 151	$ 51	$ 431	$ 310
Effective income tax rate	19.00%	11.00%	21.00%	20.00%
Favorable net discrete items, percentage impact	3.00%	12.00%	1.00%	3.00%
Favorable net discrete tax impact	$ 24	$ 57