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
Beginning Balance (Previously Reported) at Dec. 31, 2016				$ 5,037	$ 1,693
Beginning Balance at Dec. 31, 2016		$ 397	$ 1,252	5,037	1,693	$ (1,319)
Share-based awards		0	(18)			17
Share-based compensation			8
Other			1			1
Net Income (Loss)	$ 201			201
Dividends declared				(82)
Other comprehensive income (loss)	87				87
Shares acquired - share repurchase authorization						(15)
Shares acquired - share-based compensation plans						(4)
Ending Balance at Mar. 31, 2017	7,256	$ 397	1,243	5,156	1,780	(1,320)
Beginning Balance (in shares) at Dec. 31, 2016		164.4
Share-based awards (in shares)		0.5
Shares acquired - share repurchase authorization (in shares)		(0.2)
Shares acquired - share-based compensation plans (in shares)		(0.1)
Stock Issued During Period, Shares, Other		0.0
Ending Balance (in shares) at Mar. 31, 2017		164.6
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax	0
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax					(2,503)
Beginning Balance (Previously Reported) at Dec. 31, 2017				5,180	2,788
Beginning Balance at Dec. 31, 2017	8,243	$ 397	1,265	7,683	285	(1,387)
Share-based awards		0	(17)			14
Share-based compensation			9
Other			1			1
Net Income (Loss)	(31)			(31)
Dividends declared				(87)
Other comprehensive income (loss)	(170)				(170)
Shares acquired - share repurchase authorization						(15)
Shares acquired - share-based compensation plans						(2)
Ending Balance at Mar. 31, 2018	$ 7,946	$ 397	$ 1,258	7,565	115	$ (1,389)
Beginning Balance (in shares) at Dec. 31, 2017	198.3	163.9
Share-based awards (in shares)		0.4
Shares acquired - share repurchase authorization (in shares)		(0.2)
Shares acquired - share-based compensation plans (in shares)		0.0
Stock Issued During Period, Shares, Other		0.0
Ending Balance (in shares) at Mar. 31, 2018	198.3	164.1
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax	$ 2,503			$ 2,503	$ (2,503)