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
Beginning Balance (shares) at Dec. 31, 2021			84,920,965
Beginning Balance at Dec. 31, 2021		$ 5,012		$ 1,415	$ 3,478	$ 119
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	$ 290	290			290
Other comprehensive income		(250)				(250)
Dividends		(217)			(217)
Shares issued:
Exercise of stock options (shares)			105,404
Exercise of stock options		4		4
Restricted stock awards (shares)			151,080
Other benefit plans (shares)			10,607
Other benefit plans		1		1
Dividend reinvestment plan (shares)			6,282
Dividend reinvestment plan		1		1
Stock-based compensation expense		6		6
Shares acquired and retired (shares)			(35,201)
Shares acquired and retired		(5)		(1)	(4)
Shares exchanged — benefit plans (shares)			(47,909)
Shares exchanged — benefit plans		(7)		(1)	(6)
Forfeitures of restricted stock (shares)			(8,399)
Ending Balance (shares) at Mar. 31, 2022			85,102,829
Ending Balance at Mar. 31, 2022		4,835		1,425	3,541	(131)
Beginning Balance (shares) at Dec. 31, 2022	85,204,006		85,204,006
Beginning Balance at Dec. 31, 2022		4,052		1,453	3,142	(543)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	$ 212	212			212
Other comprehensive income		92				92
Dividends		(394)			(394)
Shares issued:
Exercise of stock options (shares)			64,339
Exercise of stock options		3		3
Restricted stock awards (shares)			147,169
Other benefit plans (shares)			12,299
Other benefit plans		2		2
Dividend reinvestment plan (shares)			10,911
Dividend reinvestment plan		1		1
Stock-based compensation expense		5		5
Shares acquired and retired (shares)			(199,762)
Shares acquired and retired		(24)		(4)	(20)
Shares exchanged — benefit plans (shares)			(55,382)
Shares exchanged — benefit plans		(8)		(1)	(7)
Forfeitures of restricted stock (shares)			(11,922)
Ending Balance (shares) at Mar. 31, 2023	85,171,658		85,171,658
Ending Balance at Mar. 31, 2023		$ 3,941		$ 1,459	$ 2,933	$ (451)