Consolidated Balance Sheet (parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Financing Receivable, Allowance for Credit Loss	$ (984)	$ (1,061)	$ (1,305)	$ (1,314)	$ (1,285)	$ (513)