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]	As Previously Reported [Member] Retained Earnings [Member]	As Previously Reported [Member] Accumulated Other Comprehensive Loss [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-02 [Member]					$ 0
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-01, Equity Investments Previously Classified as Available-for-sale [Member]					(4)	$ 4
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-01, Equity Investments Previously Measured at Cost [Member]					10
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2018-02 [Member]					91	(91)
Balance at beginning of period at Dec. 31, 2017		$ 1,265
Balance at end of period at Mar. 31, 2018	$ 19,683	1,265
Balance at beginning of period at Dec. 31, 2017			$ 0	$ 18,130	1,227	(518)	$ 1,130	$ (431)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent				0
Employee benefit plans				(3)
Net income (loss)	(238)				(238)
Other comprehensive income (loss), net of tax	(180)					(180)
Balance at end of period at Mar. 31, 2018	18,418		0	18,127	989	(698)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-02 [Member]					27
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-01, Equity Investments Previously Classified as Available-for-sale [Member]					0	0
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2016-01, Equity Investments Previously Measured at Cost [Member]					0
Cumulative effect of new accounting principle in period of adoption | Accounting Standards Update 2018-02 [Member]					0	0
Balance at beginning of period at Dec. 31, 2018	20,506	1,265
Balance at end of period at Mar. 31, 2019	18,321	$ 1,265
Balance at beginning of period at Dec. 31, 2018	19,241		0	18,136	1,498	(366)	$ 1,471
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent				2,400
Employee benefit plans				0
Net income (loss)	109				109
Other comprehensive income (loss), net of tax	79					79
Balance at end of period at Mar. 31, 2019	$ 17,056		$ 0	$ 15,736	$ 1,607	$ (287)