Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock, at cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2018	$ 20,670	$ 2,793	$ 15	$ 4,499	$ 17,329	$ (3,714)	$ (252)
Beginning balance (shares) at Dec. 31, 2018			1,488
Increase (Decrease) in Stockholders' Equity
Net income	964				964
Other comprehensive income (loss), net of tax	181						181
Dividends declared on preferred stock	(34)				(34)
Dividends declared on common stock	(228)				(228)
Stock option exercises and other	26			(14)		40
Share-based compensation	53			53
Other	(7)			10	(14)	(3)
Ending balance (shares) at Mar. 31, 2019			1,488
Ending balance at Mar. 31, 2019	21,625	2,793	$ 15	4,548	18,017	(3,677)	(71)
Beginning balance at Dec. 31, 2019	21,745	2,793	$ 15	4,656	19,960	(5,767)	88
Beginning balance (shares) at Dec. 31, 2019			1,488
Increase (Decrease) in Stockholders' Equity
Net income	795				795
Other comprehensive income (loss), net of tax	3,907						3,907
Dividends declared on preferred stock	(34)				(34)
Dividends declared on common stock	(233)				(233)
Stock option exercises and other	23			(8)		31
Share-based compensation	56			56
Other	11			10	(1)	2
Ending balance (shares) at Mar. 31, 2020			1,488
Ending balance at Mar. 31, 2020	$ 26,270	$ 2,793	$ 15	$ 4,714	$ 20,487	$ (5,734)	$ 3,995