Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statements of Comprehensive Income (Loss)
Net income (loss)	$ (170)	$ (146)	$ (187)	$ (244)
Unrealized gains (losses) on available-for-sale securities: [Abstract]
Unrealized gains (losses) arising during the period	46	(14)	125	(57)
Provision (benefit) for income taxes	36	0	40	5
Total	10	(14)	85	(62)
Reclassification adjustments for (gains) losses included in net income (loss)	16	0	(23)	(1)
Available-for-sale securities with other-than-temporary impairments: [Abstract]
Other-than-temporary impairments and unrealized gains (losses) arising during the period	19	17	30	23
Reclassification adjustments for (gains) losses included in net income (loss)	9	0	37	1
Foreign currency translation: [Abstract]
Foreign currency translation gains (losses)	(1)	1	0	2
Instrument-specific credit risk of liabilities measured at fair value: [Abstract]
Unrealized gains (losses) arising during the period	(2)	(18)	0	(32)
Reclassification adjustments for (gains) losses included in net income (loss)	19	0	23	0
Total other comprehensive income (loss)	70	(14)	152	(69)
Comprehensive income (loss)	$ (100)	$ (160)	$ (35)	$ (313)