Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statements of Comprehensive Income (Loss)
Net income (loss)	$ (578)	$ (359)	$ (296)
Available-for-sale securities with no credit losses:
Unrealized gains (losses) arising during the period	83	139	(60)
Provision (benefit) for income taxes	0	0	5
Total	83	139	(65)
Reclassification adjustments for (gains) losses included in net income (loss)	(19)	(13)	(5)
Available-for-sale securities with credit losses:
Unrealized gains (losses) arising during the period	0	0	41
Reclassification adjustments for (gains) losses included in net income (loss)	0	25	5
Total	0	25	5
Foreign currency translation:
Foreign currency translation gains (losses)	(3)	0	2
Total	(3)	0	2
Instrument-specific credit risk of liabilities measured at fair value:
Unrealized gains (losses) arising during the period	50	(25)	52
Reclassification adjustments for (gains) losses included in net income (loss)	6	28	0
Total other comprehensive income (loss)	117	154	30
Comprehensive income (loss)	$ (461)	$ (205)	$ (266)