Income Taxes (Income Taxes and Shareholders' Equity) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current taxes:
Federal	$ 0	$ 4	$ 4
State	1	0	1
Deferred taxes:
Federal	(1)	945	(8)
Foreign	0	(5)	2
Provision (benefit) for income taxes	0	944	(1)
Income tax effects allocated directly to equity [Abstract]
Change in unrealized gains and losses on AFS securities	5	(1)	8
Change in AFS securities with OTTI	0	1	5
Change in foreign currency translation	0	21	1
Total income taxes charged (credited) to shareholders' equity	5	21	14
Total effect of income taxes	$ 5	$ 965	$ 13