Condensed Consolidated Statements of Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common equities	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock	Previously Reported Retained Earnings	Previously Reported Accumulated Other Comprehensive Income
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax				$ 2,503	$ (2,503)
Beginning Balance at Dec. 31, 2017		$ 397	$ 1,265	7,683	285	$ (1,387)	$ 5,180	$ 2,788
Share-based awards		0	(17)			18
Share-based compensation			22
Other			3			2
Net Income	$ 739			739
Dividends declared (per share of $0.56, $0.53, $1.68 and $1.59, respectively)				(258)
Other comprehensive income (loss)	(289)				(289)
Shares acquired - share repurchase authorization						(125)
Shares acquired - share-based compensation plans						(4)
Ending Balance at Sep. 30, 2018	8,334	$ 397	1,273	8,164	(4)	(1,496)
Beginning Balance (in shares) at Dec. 31, 2017		163.9
Share-based awards (in shares)		0.6
Shares acquired - share repurchase authorization (in shares)		(1.8)
Ending Balance (in shares) at Sep. 30, 2018		162.7
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax				0	0
Beginning Balance at Jun. 30, 2018		$ 397	1,266	7,696	55	(1,498)	7,696	55
Share-based awards		0	0			2
Share-based compensation			6
Other			1			1
Net Income	553			553
Dividends declared (per share of $0.56, $0.53, $1.68 and $1.59, respectively)				(85)
Other comprehensive income (loss)	(59)				(59)
Shares acquired - share repurchase authorization						0
Shares acquired - share-based compensation plans						(1)
Ending Balance at Sep. 30, 2018	8,334	$ 397	1,273	8,164	(4)	(1,496)
Beginning Balance (in shares) at Jun. 30, 2018		162.6
Share-based awards (in shares)		0.1
Shares acquired - share repurchase authorization (in shares)		0.0
Ending Balance (in shares) at Sep. 30, 2018		162.7
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax				0	0
Beginning Balance at Dec. 31, 2018	7,833	$ 397	1,281	7,625	22	(1,492)	7,625	22
Share-based awards		0	(12)			19
Share-based compensation			23
Other			3			2
Net Income	1,371			1,371
Dividends declared (per share of $0.56, $0.53, $1.68 and $1.59, respectively)				(274)
Other comprehensive income (loss)	420				420
Shares acquired - share repurchase authorization						(5)
Shares acquired - share-based compensation plans						(9)
Ending Balance at Sep. 30, 2019	$ 9,371	$ 397	1,295	8,722	442	(1,485)
Beginning Balance (in shares) at Dec. 31, 2018	198.3	162.8
Share-based awards (in shares)		0.6
Shares acquired - share repurchase authorization (in shares)		0.0
Ending Balance (in shares) at Sep. 30, 2019	198.3	163.4
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax				0	0
Beginning Balance at Jun. 30, 2019		$ 397	1,286	8,566	364	(1,482)	$ 8,566	$ 364
Share-based awards		0	1			3
Share-based compensation			7
Other			1			1
Net Income	$ 248			248
Dividends declared (per share of $0.56, $0.53, $1.68 and $1.59, respectively)				(92)
Other comprehensive income (loss)	78				78
Shares acquired - share repurchase authorization						(5)
Shares acquired - share-based compensation plans						(2)
Ending Balance at Sep. 30, 2019	$ 9,371	$ 397	$ 1,295	$ 8,722	$ 442	$ (1,485)
Beginning Balance (in shares) at Jun. 30, 2019		163.3
Share-based awards (in shares)		0.1
Shares acquired - share repurchase authorization (in shares)		0.0
Ending Balance (in shares) at Sep. 30, 2019	198.3	163.4