Consolidated Statements Of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock	New Accounting Pronouncement, Early Adoption, Effect Retained Earnings	New Accounting Pronouncement, Early Adoption, Effect Accumulated Other Comprehensive Income
Beginning Balance at Dec. 31, 2014		$ 397	$ 1,214	$ 4,505	$ 1,744	$ (1,287)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards		0	(7)			41
Share-based compensation			20
Other			5			7
Net Income	$ 634			634
Dividends declared				(377)
Other comprehensive income (loss)	(400)				(400)
Shares acquired - share repurchase authorization						(53)
Shares acquired - share-based compensation plans						(16)
Ending Balance at Dec. 31, 2015	6,427	$ 397	1,232	4,762	1,344	(1,308)
Beginning Balance (in shares) at Dec. 31, 2014		163,700
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)		1,300
Shares acquired—share repurchase authorization (in shares)		(1,000)
Shares acquired - share-based compensation plans (in shares)		(300)
Other (in shares)		200
Ending Balance (in shares) at Dec. 31, 2015		163,900
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02							$ 0	$ 0
Share-based awards		$ 0	(8)			36
Share-based compensation			23
Other			5			5
Net Income	591			591
Dividends declared				(316)
Other comprehensive income (loss)	349				349
Shares acquired - share repurchase authorization						(39)
Shares acquired - share-based compensation plans						(13)
Ending Balance at Dec. 31, 2016	$ 7,060	$ 397	1,252	5,037	1,693	(1,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)		1,000
Shares acquired—share repurchase authorization (in shares)		(500)
Shares acquired - share-based compensation plans (in shares)		(200)
Other (in shares)		200
Ending Balance (in shares) at Dec. 31, 2016	198,300	164,400
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02							0	0
Share-based awards		$ 0	(18)			26
Share-based compensation			26
Other			5			5
Net Income	$ 1,045			1,045
Dividends declared				(410)
Other comprehensive income (loss)	603				603
Shares acquired - share repurchase authorization						(92)
Shares acquired - share-based compensation plans						(7)
Ending Balance at Dec. 31, 2017	$ 8,243	$ 397	$ 1,265	$ 5,180	$ 2,788	$ (1,387)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)	527	800
Shares acquired—share repurchase authorization (in shares)		(1,300)
Shares acquired - share-based compensation plans (in shares)		(100)
Other (in shares)		100
Ending Balance (in shares) at Dec. 31, 2017	198,300	163,900
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02							$ (492)	$ 492