Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statements of Comprehensive Income (Loss)
Net income (loss)	$ (359)	$ (296)	$ (1,605)
Unrealized gains (losses) on available-for-sale securities: [Abstract]
Unrealized gains (losses) arising during the period	139	(60)	(22)
Provision (benefit) for income taxes	0	5	(1)
Total	139	(65)	(21)
Reclassification adjustments for (gains) losses included in net income (loss)	(13)	(5)	2
Available-for-sale securities with other-than-temporary impairments: [Abstract]
Other-than-temporary impairments and unrealized gains (losses) arising during the period	0	41	(3)
Reclassification adjustments for (gains) losses included in net income (loss)	25	5	7
Provision (benefit) for income taxes	0	0	1
Total	25	5	6
Foreign currency translation: [Abstract]
Foreign currency translation gains (losses)	0	2	146
Provision (benefit) for income taxes	0	0	21
Total	0	2	125
Instrument-specific credit risk of liabilities measured at fair value: [Abstract]
Unrealized gains (losses) arising during the period	(25)	52	0
Reclassification adjustments for (gains) losses included in net income (loss)	28	0	0
Total other comprehensive income (loss)	154	30	109
Comprehensive income (loss)	$ (205)	$ (266)	$ (1,496)