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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting for equity securities as of January 1, 2018				$ 0	$ 0
Adjusted beginning of year				5,037	1,693
Beginning Balance at Dec. 31, 2016		$ 397	$ 1,252	5,037	1,693	$ (1,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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)
Beginning Balance (in shares) at Dec. 31, 2016		164,400
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)		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		163,900
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting for equity securities as of January 1, 2018				2,503	(2,503)
Adjusted beginning of year				7,683	285
Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02							$ (492)	$ 492
Share-based awards		$ 0	(17)			21
Share-based compensation			28
Other			5			4
Net Income	287			287
Dividends declared				(345)
Other comprehensive income (loss)	(263)				(263)
Shares acquired - share repurchase authorization						(125)
Shares acquired - share-based compensation plans						(5)
Ending Balance at Dec. 31, 2018	$ 7,833	$ 397	1,281	7,625	22	(1,492)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)		700
Shares acquired—share repurchase authorization (in shares)		(1,800)
Shares acquired - share-based compensation plans (in shares)		0
Other (in shares)		0
Ending Balance (in shares) at Dec. 31, 2018	198,300	162,800
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting for equity securities as of January 1, 2018	$ 2,503			0	0
Adjusted beginning of year				7,625	22
Adjustment to reclassify certain tax effects from AOCI to retained earnings | Accounting Standards Update 2018-02							0	0
Share-based awards		$ 0	(12)			21
Share-based compensation			30
Other			7			3
Net Income	1,997			1,997
Dividends declared				(365)
Other comprehensive income (loss)	426				426
Shares acquired - share repurchase authorization						(67)
Shares acquired - share-based compensation plans						(9)
Ending Balance at Dec. 31, 2019	$ 9,864	$ 397	$ 1,306	$ 9,257	$ 448	$ (1,544)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)	493	700
Shares acquired—share repurchase authorization (in shares)		(600)
Shares acquired - share-based compensation plans (in shares)		(100)
Other (in shares)		100
Ending Balance (in shares) at Dec. 31, 2019	198,300	162,900
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