Income Taxes (Income Taxes and Shareholders' Equity) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current taxes:
Federal	$ 4	$ 0	$ 0
State	1	1	10
Foreign	0	2	12
Deferred taxes:
Federal	(8)	97	48
State	0	0	0
Foreign	2	9	2
Provision (benefit) for income taxes	(1)	109	72
Income tax effects allocated directly to equity [Abstract]
Change in unrealized gains and losses on AFS securities	8	(30)	89
Change in AFS securities with OTTI	5	0	(29)
Change in foreign currency translation	1	(14)	(13)
Share-based compensation	0	9	2
Total income taxes charged (credited) to shareholders' equity	14	(35)	49
Total effect of income taxes	$ 13	$ 74	$ 121