Accumulated Other Comprehensive Income (Details Of The Reclassification From AOCI) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net gains (losses) on financial instruments at fair value and foreign exchange	$ (24)	$ 84	$ 63
Income (loss) before income taxes	(661)	(339)	289
Provision (benefit) for income taxes	944	(1)	109
Net income (loss)	(1,605)	(338)	180
Amounts reclassified from AOCI [Member]
Net income (loss)	(8)	(1)	1
Unrealized gains (losses) on AFS, net [Member] | Amounts reclassified from AOCI [Member]
Net gains (losses) on financial instruments at fair value and foreign exchange	3	7	11
Other-than-temporary impairments recognized in accumulated other comprehensive income (loss)	(7)	(4)	(4)
Net investment income	(5)	(6)	(4)
Income (loss) before income taxes	(9)	(3)	3
Provision (benefit) for income taxes	$ (1)	$ (2)	$ 2