Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total		Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 167				$ 166		$ 1
Balance, beginning at Dec. 31, 2017	18,355		$ 148	$ 8,197	10,936	$ (1,026)	100
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss), net of tax	(241)					(241)
Adjustments to Additional Paid in Capital, Share-based Compensation, Restricted Stock Unit or Restricted Stock Award, Requisite Service Period Recognition	14			14	0
Other	(2)		0	(21)	(1)	21	(1)
Balance, ending at Mar. 31, 2018	18,293		148	8,190	11,101	(1,246)	100
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity, Period Increase (Decrease)	(62)		0	(7)	165	(220)	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	179				184		(5)
Balance, beginning at Dec. 31, 2018	16,580		132	8,176	9,524	(1,324)	72
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss), net of tax	183					183
Adjustments to Additional Paid in Capital, Share-based Compensation, Restricted Stock Unit or Restricted Stock Award, Requisite Service Period Recognition	17			17	0
Other	5	[1]	0	0	5	0	0
Balance, ending at Mar. 31, 2019	16,964		132	8,193	9,713	(1,141)	67
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity, Period Increase (Decrease)	$ 384		$ 0	$ 17	$ 189	$ 183	$ (5)

[1] For additional information on other, see Note 10