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Employee Incentive Plans (Share Grants And Fair Value) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended				128 Months Ended	164 Months Ended
	Sep. 30, 2021	Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2020
Employee Incentive Plans [Abstract]
Shares granted		1,229,177	[1]	1,374,217	1,146,267	24,497,626
Fair Value - Date of Grant		$ 71		$ 65	$ 62	$ 561	$ 71
Shares Granted IPO to Date							28,247,287
Fair Value - Date of Grant IPO to Date							$ 759
Stock Incentive Plan Granted Shares Adjustment	7,034
[1] Stock Incentive Plan number of granted restricted stock units related to 2020 was adjusted by 7,034 additional restricted stock units during the nine months ended September 30, 2021.

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