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	Cumulative effect adjustment in period of adoption Retained Earnings
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	5,665	5,665		1,346	3,875	444	0
Net earnings (losses) attributable to parent	329	329			329
Net earnings (losses) including portion attributable to nonredeemable noncontrolling interest	329						0
Other comprehensive income (loss), attributable to parent		396				396
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	396
Dividends	(36)	(36)			(36)
Shares issued:
Exercise of stock options, shares			152,253
Exercise of stock options	6	6		6
Restricted stock awards, shares			232,565
Other benefit plans, shares			11,062
Other benefit plans	1	1		1
Dividend reinvestment plan, shares			1,893
Stock-based compensation expense	6	6		6
Shares exchanged — benefit plans, shares			(43,470)
Shares exchanged — benefit plans	(4)	(4)		(1)	(3)
Forfeitures of restricted stock, shares			(8,314)
Other	(5)	(3)			(3)		(2)
Ending Balance, shares at Mar. 31, 2019			89,637,713
Ending Balance at Mar. 31, 2019	5,665	5,665		1,346	3,875	444	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	(3)
Other	3
Ending Balance, Redeemable Noncontrolling Interests at Mar. 31, 2019	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	5,665	5,665		1,346	3,875	444	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	5,047	5,047		1,399	3,616	32	0
Cumulative effect of accounting change | Accounting Standards Update 2016-13								$ 7
Net earnings (losses) attributable to parent	(301)	(301)			(301)
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
Dividend reinvestment plan	0	0		0
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		89,827,336
Ending Balance at Mar. 31, 2020	$ 5,047	5,047		1,399	3,616	32	0
Ending Balance (Accounting Standards Update 2016-13) at Mar. 31, 2020								7
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 | Accounting Standards Update 2016-13								$ 7