Employee Benefit Plans - Severance Accrual (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period	$ 24
Accruals	165
Benefit payments	(102)
Balance at end of period	87
Employee Severance [Member] | Short term supplemental unemployment benefits [Member]
Restructuring Cost and Reserve [Line Items]
Balance at end of period	$ 51