Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statements of Comprehensive Income (Loss)
Net income (loss)	$ (267)	$ 31	$ (1,568)	$ (73)
Unrealized gains (losses) on available-for-sale securities: [Abstract]
Unrealized gains (losses) arising during the period	16	(20)	20	204
Provision (benefit) for income taxes	7	(7)	7	72
Total	9	(13)	13	132
Reclassification adjustments for (gains) losses included in net income (loss)	1	(1)	(4)	7
Provision (benefit) for income taxes	(1)	(1)	(1)	2
Total	2	0	(3)	5
Available-for-sale securities with other-than-temporary impairments: [Abstract]
Other-than-temporary impairments and unrealized gains (losses) arising during the period	40	0	6	7
Provision (benefit) for income taxes	2	0	2	2
Total	38	0	4	5
Reclassification adjustments for (gains) losses included in net income (loss)	4	0	6	0
Provision (benefit) for income taxes	1	0	2	0
Total	3	0	4	0
Foreign currency translation: [Abstract]
Foreign currency translation gains (losses)	1	(15)	145	(70)
Provision (benefit) for income taxes	(1)	(5)	20	(24)
Total	2	(10)	125	(46)
Total other comprehensive income (loss)	54	(23)	143	96
Comprehensive income (loss)	$ (213)	$ 8	$ (1,425)	$ 23