Investments (Narrative) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014 Security	Sep. 30, 2013	Sep. 30, 2014 Security	Sep. 30, 2013	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Non-cash exchange of securities	$ 219,000,000
Fair value of securities transferred from AFS to HTM	2,000,000,000		2,000,000,000
Net unrealized appreciation (depreciation) included in OCI	(1,000,000)	1,000,000	(6,000,000)	(24,000,000)
Net unrealized depreciation included in AOCI					4,000,000
Percentage of mortgage-backed securities represented by investments in US government agency bonds	83.00%		83.00%		83.00%
Credit losses recognized in net income for corporate securities	4,000,000	1,000,000	14,000,000	8,000,000
Credit losses recognized in net income for mortgage-backed securities	0	0	0	0
Number of fixed maturities in an unrealized loss position	5,799		5,799
Total number of fixed maturities	25,735		25,735
Largest single unrealized loss in the fixed maturities	3,000,000		3,000,000
Number of equity securities in an unrealized loss position	64		64
Total number of equity securities	238		238
Largest single unrealized loss in the equity securities	1,000,000		1,000,000
Restricted assets in fixed maturities and short-term investments	15,700,000,000		15,700,000,000		16,300,000,000
Restricted assets in cash	$ 72,000,000		$ 72,000,000		$ 162,000,000
Moodys Historical Mean Recovery Rate			42.00%
Company Assumed Recovery Rate			32.00%