CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Millions	Total		Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption	$ 0	[1]				$ 0	$ 0
Reclassification from retained earnings of cumulative effect adjustment to initially apply new accounting guidance for financial liabilities measured under the fair value option, net of tax	0	[1]				0	0
Balance at beginning of period at Dec. 31, 2014			$ 1,565
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock issuance			0
Preferred stock redemption			(300)
Balance at end of period at Dec. 31, 2015	20,525		$ 1,265
Balance at beginning of period at Dec. 31, 2014				$ 0	$ 14,170	1,233	(1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contribution from parent					4,000
Employee benefit plans					(1)
Net income (loss)	330					330
Cash dividends declared on preferred stock						(65)
Other comprehensive income (loss), net of tax	(406)						(406)
Balance at end of period (As Previously Reported [Member]) at Dec. 31, 2015						1,498	(407)
Balance at end of period at Dec. 31, 2015	19,260			$ 0	18,169	1,498	(407)
Number of shares at beginning of period at Dec. 31, 2014			25,947,500	713
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of shares of preferred stock issued to parent			0	1
Number of shares of preferred stock redeemed			(4,500,000)
Number of shares at end of period at Dec. 31, 2015			21,447,500	714
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption	0	[1]				0	0
Reclassification from retained earnings of cumulative effect adjustment to initially apply new accounting guidance for financial liabilities measured under the fair value option, net of tax	0	[1]				0	0
Preferred stock issuance			$ 1,265
Preferred stock redemption			(1,265)
Balance at end of period at Dec. 31, 2016	20,355		$ 1,265
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contribution from parent					0
Employee benefit plans					(21)
Net income (loss)	129					129
Cash dividends declared on preferred stock						(67)
Other comprehensive income (loss), net of tax	(211)						(211)
Balance at end of period (As Previously Reported [Member]) at Dec. 31, 2016						1,560	(618)
Balance at end of period at Dec. 31, 2016	19,090			$ 0	18,148	1,386	(444)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of shares of preferred stock issued to parent			1,265	0
Number of shares of preferred stock redeemed			(21,447,500)
Number of shares at end of period at Dec. 31, 2016			1,265	714
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption	174	[1]				(174)	174
Reclassification from retained earnings of cumulative effect adjustment to initially apply new accounting guidance for financial liabilities measured under the fair value option, net of tax	174	[1]				(174)	174
Preferred stock issuance			$ 0
Preferred stock redemption			0
Balance at end of period at Dec. 31, 2017	20,094		$ 1,265
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contribution from parent					0
Employee benefit plans					(18)
Net income (loss)	(179)					(179)
Cash dividends declared on preferred stock						(77)
Other comprehensive income (loss), net of tax	13						13
Balance at end of period at Dec. 31, 2017	$ 18,829			$ 0	$ 18,130	$ 1,130	$ (431)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of shares of preferred stock issued to parent			0	0
Number of shares of preferred stock redeemed			0
Number of shares at end of period at Dec. 31, 2017			1,265	714

[1] See Note 2, "Summary of Significant Accounting Polices and New Accounting Pronouncements," for additional discussion.