Investments (Narrative) (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Security	Jun. 30, 2013	Jun. 30, 2014 Security	Jun. 30, 2013	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Net unrealized appreciation (depreciation) included in OCI	$ 1,000,000	$ 1,000,000	$ 5,000,000	$ 25,000,000
Net unrealized depreciation included in AOCI	1,000,000		1,000,000		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	6,000,000	6,000,000	10,000,000	7,000,000
Credit losses recognized in net income for mortgage-backed securities	0	0
Number of fixed maturities in an unrealized loss position	3,253		3,253
Total number of fixed maturities	25,285		25,285
Largest single unrealized loss in the fixed maturities	3,000,000		3,000,000
Number of equity securities in an unrealized loss position	52		52
Total number of equity securities	186		186
Largest single unrealized loss in the equity securities	42,000,000		42,000,000
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	$ 84,000,000		$ 84,000,000		$ 162,000,000
Moodys Historical Mean Recovery Rate			42.00%
Company Assumed Recovery Rate			32.00%
Unrealized Loss as a Percentage of Amortized Cost	8.00%		8.00%