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
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
Increase to allowance through retained earnings for ASU 2016-13, after-tax				0
Beginning Balance at Dec. 31, 2017		$ 397	$ 1,265	5,180	2,788	$ (1,387)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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)
Beginning Balance (in shares) at Dec. 31, 2017		163,900
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		162,800
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				7,625	22
Increase to allowance through retained earnings for ASU 2016-13, after-tax				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)		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		162,900
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				9,255	448
Increase to allowance through retained earnings for ASU 2016-13, after-tax	(2)			(2)
Share-based awards		$ 0	(15)			15
Share-based compensation			31
Other			6			5
Net Income	1,216			1,216
Dividends declared				(386)
Other comprehensive income (loss)	321				321
Shares acquired - share repurchase authorization						(261)
Shares acquired - share-based compensation plans						(5)
Ending Balance at Dec. 31, 2020	$ 10,789	$ 397	$ 1,328	$ 10,085	$ 769	$ (1,790)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based awards (in shares)	274	500
Shares acquired—share repurchase authorization (in shares)		(2,500)
Shares acquired - share-based compensation plans (in shares)		(100)
Other (in shares)		100
Ending Balance (in shares) at Dec. 31, 2020		160,900