Investments (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013 partnerships Security	Dec. 31, 2012	Dec. 31, 2011
Investments, Debt and Equity Securities [Abstract]
Net unrealized appreciation (depreciation) included in OCI	$ 25,000,000	$ 137,000,000
Net unrealized depreciation included in AOCI	(4,000,000)	(25,000,000)
Percentage of mortgage-backed securities represented by investments in US government agency bonds	83.00%	85.00%
Portion of gross unrealized loss represented by the United States Treasury and Agency obligations	425,000,000
Company assumed recovery rate	32.00%
Moodys historical mean recovery rate	42.00%
Credit losses recognized in net income for corporate securities	11,000,000	14,000,000	9,000,000
Credit losses recognized in net income for mortgage-backed securities	1,000,000	6,000,000	11,000,000
Limited partnerships number	62
Trading securities - mutual funds	246,000,000	212,000,000
Trading securities - equity securities	23,000,000	23,000,000
Trading securities - fixed maturities	7,000,000	8,000,000
Number of fixed maturities in an unrealized loss position	6,161
Total number of fixed maturities	25,062
Largest single unrealized loss in the fixed maturities	(6,000,000)
Number of equity securities in an unrealized loss position	71
Total number of equity securities	185
Largest single unrealized loss in the equity securities	(58,000,000)
Restricted assets in fixed maturities and short-term investments	16,300,000,000	16,600,000,000
Restricted assets in cash	$ 162,000,000	$ 139,000,000