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
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (losses) attributable to parent	(124)	(124)			(124)
Net Income (Loss) Attributable to Noncontrolling Interest	(13)
Net earnings (loss), including noncontrolling interests	(137)
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	(124)						0
Other comprehensive income (loss), attributable to parent		190				190
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	190
Dividends	(81)	(81)			(81)
Shares issued:
Exercise of stock options, shares			209,343
Exercise of stock options	9	9		9
Restricted stock awards, shares			227,867
Other benefit plans, shares			66,496
Other benefit plans	5	5		5
Dividend reinvestment plan, shares			4,350
Stock-based compensation expense	10	10		10
Shares acquired and retired, shares			(2,020,519)
Shares acquired and retired	(137)	(137)		(31)	(106)
Shares exchanged — benefit plans, shares			(96,394)
Shares exchanged — benefit plans	(11)	(11)		(2)	(9)
Forfeitures of restricted stock, shares			(35,422)
Other	(11)	(11)			(11)		0
Ending Balance, shares at Jun. 30, 2020			88,659,407
Ending Balance at Jun. 30, 2020	6,126	6,126		1,388	3,685	1,053	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	(13)
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	2
Other	11
Ending Balance, Redeemable Noncontrolling Interests at Jun. 30, 2020	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	5,047	5,047		1,399	3,616	32	0
Beginning Balance, shares at Mar. 31, 2020			89,827,336
Beginning Balance at Mar. 31, 2020	5,047	5,047		1,399	3,616	32	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (losses) attributable to parent	177	177			177
Net Income (Loss) Attributable to Noncontrolling Interest	(10)
Net earnings (loss), including noncontrolling interests	167
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	177						0
Other comprehensive income (loss), attributable to parent		1,021				1,021
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	1,021
Dividends	(41)	(41)			(41)
Shares issued:
Exercise of stock options, shares			5,250
Exercise of stock options	0	0		0
Restricted stock awards, shares			0
Other benefit plans, shares			51,955
Other benefit plans	4	4		4
Dividend reinvestment plan, shares			2,733
Stock-based compensation expense	4	4		4
Shares acquired and retired, shares			(1,194,236)
Shares acquired and retired	(76)	(76)		(19)	(57)
Shares exchanged — benefit plans, shares			(540)
Shares exchanged — benefit plans	0	0		0	0
Forfeitures of restricted stock, shares			(33,091)
Other, shares			0
Other	(10)	(10)			(10)		0
Ending Balance, shares at Jun. 30, 2020			88,659,407
Ending Balance at Jun. 30, 2020	6,126	6,126		1,388	3,685	1,053	0
Beginning Balance, Redeemable Noncontrolling Interests at Mar. 31, 2020	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Net earnings attributable to redeemable noncontrolling interests	(10)
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	0
Other	10
Ending Balance, Redeemable Noncontrolling Interests at Jun. 30, 2020	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,126	6,126		1,388	3,685	1,053	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]
Net earnings (losses) attributable to parent	1,421	1,421			1,421
Net Income (Loss) Attributable to Noncontrolling Interest	0						0
Net earnings (loss), including noncontrolling interests	1,421
Other comprehensive income (loss), attributable to parent		(1,083)				(1,083)
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	(1,083)
Dividends	(1,275)	(1,275)			(1,275)
Shares issued:
Exercise of stock options, shares			964,744
Exercise of stock options	49	49		49
Restricted stock awards, shares			207,020
Other benefit plans, shares			43,465
Other benefit plans	5	5		5
Dividend reinvestment plan, shares			36,654
Dividend reinvestment plan	4	4		4
Stock-based compensation expense	7	7		7
Shares acquired and retired, shares			(2,674,222)
Shares acquired and retired	(306)	(306)		(43)	(263)
Shares exchanged — benefit plans, shares			(91,364)
Shares exchanged — benefit plans	$ (10)	(10)		(1)	(9)
Forfeitures of restricted stock, shares			(117,616)
Ending Balance, shares at Jun. 30, 2021	84,713,927		84,713,927
Ending Balance at Jun. 30, 2021	$ 5,601	5,601		1,388	4,023	190	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,685	6,685		1,364	4,354	967	0
Beginning Balance, shares at Mar. 31, 2021			85,126,062
Beginning Balance at Mar. 31, 2021	6,685	6,685		1,364	4,354	967	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (losses) attributable to parent	1,002	1,002			1,002
Net Income (Loss) Attributable to Noncontrolling Interest	0						0
Net earnings (loss), including noncontrolling interests	1,002
Other comprehensive income (loss), attributable to parent		(777)				(777)
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	(777)
Dividends	(1,232)	(1,232)			(1,232)
Shares issued:
Exercise of stock options, shares			561,732
Exercise of stock options	30	30		30
Restricted stock awards, shares			0
Other benefit plans, shares			27,833
Other benefit plans	3	3		3
Dividend reinvestment plan, shares			34,348
Dividend reinvestment plan	4	4		4
Stock-based compensation expense	2	2		2
Shares acquired and retired, shares			(916,520)
Shares acquired and retired	(114)	(114)		(15)	(99)
Shares exchanged — benefit plans, shares			(14,380)
Shares exchanged — benefit plans	$ (2)	(2)		0	(2)
Forfeitures of restricted stock, shares			(105,148)
Ending Balance, shares at Jun. 30, 2021	84,713,927		84,713,927
Ending Balance at Jun. 30, 2021	$ 5,601	5,601		1,388	4,023	190	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 5,601	$ 5,601		$ 1,388	$ 4,023	$ 190	$ 0