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
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	6,321	4,970		1,334	4,022	917	2
Net earnings (losses) attributable to parent	686	686			686
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	686						0
Other comprehensive income (loss), attributable to parent		869				869
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	869
Dividends	(242)	(242)			(242)
Shares issued:
Exercise of stock options, shares			591,233
Exercise of stock options	25	25		25
Restricted stock awards, shares			232,635
Other benefit plans, shares			58,488
Other benefit plans	6	6		6
Dividend reinvestment plan, shares			11,059
Dividend reinvestment plan	1	1		1
Stock-based compensation expense	17	17		17
Shares exchanged — benefit plans, shares			(47,069)
Shares exchanged — benefit plans	(5)	(5)		(1)	(4)
Forfeitures of restricted stock, shares			(10,647)
Other	(8)	(6)			(6)		(2)
Ending Balance, shares at Sep. 30, 2019			90,127,423
Ending Balance at Sep. 30, 2019	6,321	6,321		1,382	4,022	917	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	(8)
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	2
Other	6
Ending Balance, Redeemable Noncontrolling Interests at Sep. 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
Beginning Balance, shares at Jun. 30, 2019			89,917,601
Beginning Balance at Jun. 30, 2019	6,090	6,090		1,367	3,914	809	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,321	6,321		1,382	4,022	917	0
Net earnings (losses) attributable to parent	147	147			147
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	147						0
Other comprehensive income (loss), attributable to parent		108				108
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	108
Dividends	(36)	(36)			(36)
Shares issued:
Exercise of stock options, shares			191,227
Exercise of stock options	8	8		8
Restricted stock awards, shares			70
Other benefit plans, shares			17,345
Other benefit plans	2	2		2
Dividend reinvestment plan, shares			1,570
Dividend reinvestment plan	0	0		0
Stock-based compensation expense	5	5		5
Shares exchanged — benefit plans, shares			(80)
Shares exchanged — benefit plans	0	0		0	0
Forfeitures of restricted stock, shares			(310)
Other	(3)	(3)			(3)		0
Ending Balance, shares at Sep. 30, 2019			90,127,423
Ending Balance at Sep. 30, 2019	6,321	6,321		1,382	4,022	917	0
Beginning Balance, Redeemable Noncontrolling Interests at Jun. 30, 2019	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 Sep. 30, 2019	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,321	6,321		1,382	4,022	917	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	863	0
Net earnings (losses) attributable to parent	40	40			40
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	40						0
Other comprehensive income (loss), attributable to parent		366				366
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	366
Dividends	(120)	(120)			(120)
Shares issued:
Exercise of stock options, shares			229,208
Exercise of stock options	10	10		10
Restricted stock awards, shares			227,867
Other benefit plans, shares			105,318
Other benefit plans	7	7		7
Dividend reinvestment plan, shares			7,251
Dividend reinvestment plan	1	1		1
Stock-based compensation expense	15	15		15
Shares acquired and retired, shares			(3,468,107)
Shares acquired and retired	(233)	(233)		(54)	(179)
Shares exchanged — benefit plans, shares			(97,731)
Shares exchanged — benefit plans	(11)	(11)		(2)	(9)
Forfeitures of restricted stock, shares			(40,910)
Other	$ (11)	(11)		(4)	(11)	4	0
Ending Balance, shares at Sep. 30, 2020	87,266,582		87,266,582
Ending Balance at Sep. 30, 2020	$ 6,340	6,340		1,370	3,737	1,233	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 Sep. 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
Beginning Balance, shares at Jun. 30, 2020			88,659,407
Beginning Balance at Jun. 30, 2020	6,126	6,126		1,388	3,685	1,053	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,126	6,340		1,370	3,737	1,233	0
Net earnings (losses) attributable to parent	164	164			164
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	164						0
Other comprehensive income (loss), attributable to parent		176				176
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	176
Dividends	(39)	(39)			(39)
Shares issued:
Exercise of stock options, shares			19,865
Exercise of stock options	1	1		1
Restricted stock awards, shares			0
Other benefit plans, shares			38,822
Other benefit plans	2	2		2
Dividend reinvestment plan, shares			2,901
Dividend reinvestment plan	1	1		1
Stock-based compensation expense	5	5		5
Shares acquired and retired, shares			(1,447,588)
Shares acquired and retired	(96)	(96)		(23)	(73)
Shares exchanged — benefit plans, shares			(1,337)
Shares exchanged — benefit plans	0	0		0	0
Forfeitures of restricted stock, shares			(5,488)
Other	$ 0			(4)	0	4	0
Ending Balance, shares at Sep. 30, 2020	87,266,582		87,266,582
Ending Balance at Sep. 30, 2020	$ 6,340	6,340		1,370	3,737	1,233	0
Beginning Balance, Redeemable Noncontrolling Interests at Jun. 30, 2020	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Net earnings attributable to redeemable noncontrolling interests	0
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	0
Other	0
Ending Balance, Redeemable Noncontrolling Interests at Sep. 30, 2020	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 6,340	$ 6,340		$ 1,370	$ 3,737	$ 1,233	$ 0