Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statements of Comprehensive Income (Loss)
Net income (loss)	$ (45)	$ (267)	$ (289)	$ (1,568)
Unrealized gains (losses) on available-for-sale securities: [Abstract]
Unrealized gains (losses) arising during the period	(4)	16	(61)	20
Provision (benefit) for income taxes	0	7	5	7
Total	(4)	9	(66)	13
Reclassification adjustments for (gains) losses included in net income (loss)	(2)	1	(3)	(4)
Provision (benefit) for income taxes	0	(1)	0	(1)
Total	(2)	2	(3)	(3)
Available-for-sale securities with other-than-temporary impairments: [Abstract]
Other-than-temporary impairments and unrealized gains (losses) arising during the period	25	40	48	6
Provision (benefit) for income taxes	0	2	0	2
Total	25	38	48	4
Reclassification adjustments for (gains) losses included in net income (loss)	2	4	3	6
Provision (benefit) for income taxes	0	1	0	2
Total	2	3	3	4
Foreign currency translation: [Abstract]
Foreign currency translation gains (losses)	0	1	2	145
Provision (benefit) for income taxes	0	(1)	0	20
Total	0	2	2	125
Instrument-specific credit risk of liabilities measured at fair value: [Abstract]
Net gains (losses) of financial instruments at fair value	28	0	(4)	0
Provision (benefit) for income taxes	0	0	0	0
Total	28	0	(4)	0
Total other comprehensive income (loss)	49	54	(20)	143
Comprehensive income (loss)	$ 4	$ (213)	$ (309)	$ (1,425)