Condensed Consolidated Statements of Shareholders' Equity (Parentheticals) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13
Treasury shares held in trust (in shares)	1	1	1	1	1	1	1	1
Treasury share held in trust	$ 29	$ 29	$ 29	$ 29	$ 29	$ 29	$ 29	$ 29
Common stock	17	17	$ 17	$ 17	17	$ 17	$ 17	$ 17
Decrease in retained earnings		$ (54,264)			$ (49,640)
Accounting Standards Update 2016-13
Decrease in retained earnings	$ (3)