Consolidated Statement of Changes in Equity (Unaudited) - USD ($) $ in Millions	Total	Total	Common Shares	Common Stock and Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income	Noncontrolling interests
Beginning Balance, shares at Dec. 31, 2015			87,474,452
Beginning Balance at Dec. 31, 2015	$ 4,770	$ 4,592		$ 1,301	$ 2,987	$ 304	$ 178
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	280	264			264		16
Other comprehensive income (loss)	456	449				449	7
Dividends on Common Stock	(73)	(73)			(73)
Shares issued:
Exercise of stock options, shares			753,095
Exercise of stock options	26	26		26
Restricted stock awards, shares			318,940
Restricted stock awards	0	0		0
Other benefit plans, shares			82,087
Other benefit plans	6	6		6
Dividend reinvestment plan, shares			10,930
Dividend reinvestment plan	1	1		1
Stock-based compensation expense	22	22		22
Shares acquired and retired, shares			(1,796,009)
Shares acquired and retired	(124)	(124)		(27)	(97)
Shares exchanged — benefit plans, shares			(28,059)
Shares exchanged — benefit plans	(2)	(2)		0	(2)
Forfeitures of restricted stock, shares			(2,785)
Forfeitures of restricted stock	0	0		0
Other	(4)						(4)
Ending Balance, shares at Sep. 30, 2016			86,812,651
Ending Balance at Sep. 30, 2016	$ 5,358	5,161		1,329	3,079	753	197
Beginning Balance, shares at Dec. 31, 2016	86,924,399		86,924,399
Beginning Balance at Dec. 31, 2016	$ 4,919	4,916		1,198	3,343	375	3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	311	309			309		2
Other comprehensive income (loss)	314	314				314	0
Dividends on Common Stock	(214)	(214)			(214)
Shares issued:
Exercise of stock options, shares			870,022
Exercise of stock options	29	29		29
Restricted stock awards, shares			232,250
Restricted stock awards	0	0		0
Other benefit plans, shares			85,190
Other benefit plans	8	8		8
Dividend reinvestment plan, shares			22,243
Dividend reinvestment plan	2	2		2
Stock-based compensation expense	18	18		18
Shares exchanged — benefit plans, shares			(34,922)
Shares exchanged — benefit plans	(3)	(3)		0	(3)
Forfeitures of restricted stock, shares			(6,388)
Forfeitures of restricted stock	0	0		0
Other	$ (5)						(5)
Ending Balance, shares at Sep. 30, 2017	88,092,794		88,092,794
Ending Balance at Sep. 30, 2017	$ 5,379	$ 5,379		$ 1,255	$ 3,435	$ 689	$ 0