Income Taxes (Income Taxes and Shareholders' Equity) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current taxes:
Federal	$ 0	$ 0	$ 0
State	1	10	8
Foreign	2	12	1
Deferred taxes:
Federal	97	48	165
Foreign	9	2	(8)
Provision (benefit) for income taxes	109	72	166
Income tax effects allocated directly to equity [Abstract]
Change in unrealized gains and losses on AFS securities	(30)	89	(81)
Change in AFS securities with OTTI	0	(29)	4
Change in foreign currency translation	(14)	(13)	1
Share-based compensation	9	2	4
Total income taxes charged (credited) to shareholders' equity	(35)	49	(72)
Total effect of income taxes	$ 74	$ 121	$ 94