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	104	101			101		3
Other comprehensive income (loss)	146	144				144	2
Dividends on Common Stock	(24)	(24)			(24)
Shares issued:
Exercise of stock options, shares			279,165
Exercise of stock options	10	10		10
Restricted stock awards, shares			317,230
Restricted stock awards	0	0		0
Other benefit plans, shares			47,566
Other benefit plans	3	3		3
Dividend reinvestment plan, shares			3,736
Stock-based compensation expense	7	7		7
Shares acquired and retired, shares			(1,128,128)
Shares acquired and retired	(76)	(76)		(16)	(60)
Shares exchanged — benefit plans, shares			(27,551)
Shares exchanged — benefit plans	(2)	(2)		0	(2)
Forfeitures of restricted stock, shares			(180)
Forfeitures of restricted stock	0	0		0
Other	(1)						(1)
Ending Balance, shares at Mar. 31, 2016			86,966,290
Ending Balance at Mar. 31, 2016	$ 4,937	4,755		1,305	3,002	448	182
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	155	153			153		2
Other comprehensive income (loss)	124	124				124	0
Dividends on Common Stock	(27)	(27)			(27)
Shares issued:
Exercise of stock options, shares			411,167
Exercise of stock options	15	15		15
Restricted stock awards, shares			232,250
Restricted stock awards	0	0		0
Other benefit plans, shares			54,453
Other benefit plans	5	5		5
Dividend reinvestment plan, shares			3,277
Dividend reinvestment plan	0	0		0
Stock-based compensation expense	8	8		8
Shares exchanged — benefit plans, shares			(32,176)
Shares exchanged — benefit plans	(3)	(3)		0	(3)
Forfeitures of restricted stock, shares			(1,699)
Forfeitures of restricted stock	0	0		0
Other	$ (1)						(1)
Ending Balance, shares at Mar. 31, 2017	87,591,671		87,591,671
Ending Balance at Mar. 31, 2017	$ 5,195	$ 5,191		$ 1,226	$ 3,466	$ 499	$ 4