Consolidated Statement of Changes in Equity (Unaudited) - USD ($) $ in Millions	Total	Total	Common Shares	Common Stock and Capital Surplus	Retained Earnings	Accumulated Other Comp. Income	Noncontrolling interests	Cumulative effect adjustment in period of adoption Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 6,269	$ 6,269		$ 1,397	$ 4,009	$ 863	$ 0	$ 7
Cumulative effect of accounting change | Accounting Standards Update 2016-13								7
Beginning Balance, shares at Dec. 31, 2019			90,303,686
Beginning Balance at Dec. 31, 2019	6,269	6,269		1,397	4,009	863	0	7
Beginning Balance (Accounting Standards Update 2016-13) at Dec. 31, 2019								7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	5,047	5,047		1,399	3,616	32	0	7
Cumulative effect of accounting change | Accounting Standards Update 2016-13								$ 7
Net earnings (losses) attributable to parent	(301)	(301)			(301)
Net earnings (loss), including noncontrolling interests	(304)
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	(301)						0
Other comprehensive income (loss), attributable to parent		(831)				(831)
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	(831)
Dividends	(40)	(40)			(40)
Shares issued:
Exercise of stock options, shares			204,093
Exercise of stock options	9	9		9
Restricted stock awards, shares			227,867
Other benefit plans, shares			14,541
Other benefit plans	1	1		1
Dividend reinvestment plan, shares			1,617
Stock-based compensation expense	6	6		6
Shares acquired and retired, shares			(826,283)
Shares acquired and retired	(61)	(61)		(12)	(49)
Shares exchanged — benefit plans, shares			(95,854)
Shares exchanged — benefit plans	(11)	(11)		(2)	(9)
Forfeitures of restricted stock, shares			(2,331)
Other	(1)	(1)			(1)		0
Ending Balance, shares at Mar. 31, 2020			89,827,336
Ending Balance at Mar. 31, 2020	5,047	5,047		1,399	3,616	32	0
Beginning Balance, Redeemable Noncontrolling Interests at Dec. 31, 2019	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Net earnings attributable to redeemable noncontrolling interests	(3)
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	2
Other	1
Ending Balance, Redeemable Noncontrolling Interests at Mar. 31, 2020	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	5,047	5,047		1,399	3,616	32	0
Cumulative effect of accounting change	$ 6,789	6,789		1,367	4,149	1,273	0
Beginning Balance, shares at Dec. 31, 2020	86,345,246		86,345,246
Beginning Balance at Dec. 31, 2020	$ 6,789	6,789		1,367	4,149	1,273	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,789	6,685		1,364	4,354	967	0
Net earnings (losses) attributable to parent	419	419			419
Net earnings (loss), including noncontrolling interests	419
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest							0
Other comprehensive income (loss), attributable to parent		(306)				(306)
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	(306)
Dividends	(43)	(43)			(43)
Shares issued:
Exercise of stock options, shares			403,012
Exercise of stock options	19	19		19
Restricted stock awards, shares			207,020
Other benefit plans, shares			15,632
Other benefit plans	2	2		2
Dividend reinvestment plan, shares			2,306
Dividend reinvestment plan	0	0		0
Stock-based compensation expense	5	5		5
Shares acquired and retired, shares			(1,757,702)
Shares acquired and retired	(192)	(192)		(28)	(164)
Shares exchanged — benefit plans, shares			(76,984)
Shares exchanged — benefit plans	$ (8)	(8)		(1)	(7)
Forfeitures of restricted stock, shares			(12,468)
Ending Balance, shares at Mar. 31, 2021	85,126,062		85,126,062
Ending Balance at Mar. 31, 2021	$ 6,685	6,685		1,364	4,354	967	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 6,685	$ 6,685		$ 1,364	$ 4,354	$ 967	$ 0