Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statements of Comprehensive Income (Loss)
Net income (loss)	$ (146)	$ (1,229)	$ (244)	$ (1,301)
Unrealized gains (losses) on available-for-sale securities: [Abstract]
Unrealized gains (losses) arising during the period	(14)	44	(57)	4
Provision (benefit) for income taxes	0	6	5	0
Total	(14)	38	(62)	4
Reclassification adjustments for (gains) losses included in net income (loss)	0	(3)	(1)	(5)
Provision (benefit) for income taxes	0	1	0	0
Total	0	(4)	(1)	(5)
Available-for-sale securities with other-than-temporary impairments: [Abstract]
Other-than-temporary impairments and unrealized gains (losses) arising during the period	17	(47)	23	(34)
Provision (benefit) for income taxes	0	(5)	0	0
Total	17	(42)	23	(34)
Reclassification adjustments for (gains) losses included in net income (loss)	0	0	1	2
Provision (benefit) for income taxes	0	0	0	1
Total	0	0	1	1
Foreign currency translation: [Abstract]
Foreign currency translation gains (losses)	1	0	2	144
Provision (benefit) for income taxes	0	0	0	21
Total	1	0	2	123
Instrument-specific credit risk of liabilities measured at fair value: [Abstract]
Net gains (losses) of financial instruments at fair value	(18)	0	(32)	0
Provision (benefit) for income taxes	0	0	0	0
Total	(18)	0	(32)	0
Total other comprehensive income (loss)	(14)	(8)	(69)	89
Comprehensive income (loss)	$ (160)	$ (1,237)	$ (313)	$ (1,212)