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 (Loss)	Noncontrolling interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 4,972	$ 4,970		$ 1,334	$ 3,588	$ 48	$ 2
Beginning Balance, shares at Dec. 31, 2018			89,291,724
Beginning Balance at Dec. 31, 2018	4,972	4,970		1,334	3,588	48	2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	4,972	4,970		1,334	3,588	48	2
Net earnings (losses) attributable to parent	539	539			539
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	539						0
Other comprehensive income (loss), attributable to parent		761				761
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	761
Dividends	(206)	(206)			(206)
Shares issued:
Exercise of stock options, shares			400,006
Exercise of stock options	17	17		17
Restricted stock awards, shares			232,565
Other benefit plans, shares			41,143
Other benefit plans	4	4		4
Dividend reinvestment plan, shares			9,489
Dividend reinvestment plan	1	1		1
Stock-based compensation expense	12	12		12
Shares exchanged — benefit plans, shares			(46,989)
Shares exchanged — benefit plans	(5)	(5)		(1)	(4)
Forfeitures of restricted stock, shares			(10,337)
Other	(5)	(3)			(3)		(2)
Ending Balance, shares at Jun. 30, 2019			89,917,601
Ending Balance at Jun. 30, 2019	6,090	6,090		1,367	3,914	809	0
Beginning Balance, Redeemable Noncontrolling Interests at Dec. 31, 2018	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Net earnings attributable to redeemable noncontrolling interests	(4)
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	1
Other	3
Ending Balance, Redeemable Noncontrolling Interests at Jun. 30, 2019	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	5,665	5,665		1,346	3,875	444	0
Beginning Balance, shares at Mar. 31, 2019			89,637,713
Beginning Balance at Mar. 31, 2019	5,665	5,665		1,346	3,875	444	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,090	6,090		1,367	3,914	809	0
Net earnings (losses) attributable to parent	210	210			210
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	210						0
Other comprehensive income (loss), attributable to parent		365				365
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	365
Dividends	(170)	(170)			(170)
Shares issued:
Exercise of stock options, shares			247,753
Exercise of stock options	11	11		11
Restricted stock awards, shares			0
Other benefit plans, shares			30,081
Other benefit plans	3	3		3
Dividend reinvestment plan, shares			7,596
Dividend reinvestment plan	1	1		1
Stock-based compensation expense	6	6		6
Shares exchanged — benefit plans, shares			(3,519)
Shares exchanged — benefit plans	(1)	(1)		0	(1)
Forfeitures of restricted stock, shares			(2,023)
Other	0				0		0
Ending Balance, shares at Jun. 30, 2019			89,917,601
Ending Balance at Jun. 30, 2019	6,090	6,090		1,367	3,914	809	0
Beginning Balance, Redeemable Noncontrolling Interests at Mar. 31, 2019	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Net earnings attributable to redeemable noncontrolling interests	(1)
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	1
Other	0
Ending Balance, Redeemable Noncontrolling Interests at Jun. 30, 2019	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,090	6,090		1,367	3,914	809	0
Cumulative effect of accounting change	$ 6,269	6,269		1,397	4,009	863	0
Beginning Balance, shares at Dec. 31, 2019	90,303,686		90,303,686
Beginning Balance at Dec. 31, 2019	$ 6,269	6,269		1,397	4,009	863	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,269	6,269		1,397	4,009	1,053	0
Net earnings (losses) attributable to parent	(124)	(124)			(124)
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
Dividend reinvestment plan	0	0		0
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		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]
Cumulative effect of accounting change	5,047	6,126		1,388	3,685	1,053	0
Net earnings (losses) attributable to parent	177	177			177
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
Dividend reinvestment plan	0	0		0
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	$ (10)	(10)			(10)		0
Ending Balance, shares at Jun. 30, 2020	88,659,407		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