Investments (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014 partnerships Security	Dec. 31, 2013	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Fair value of securities transferred from AFS to HTM	$ 2,000,000,000
Transfer to Investments	219,000,000
Net unrealized appreciation (depreciation) included in OCI	4,000,000	25,000,000
Net unrealized depreciation included in AOCI	3,000,000	4,000,000
Portion of gross unrealized loss represented by the United States Treasury and Agency obligations	60,000,000
Company assumed recovery rate	32.00%
Moodys historical mean recovery rate	42.00%
Credit losses recognized in net income for corporate securities	27,000,000	11,000,000	14,000,000
Credit losses recognized in net income for mortgage-backed securities	0	1,000,000	6,000,000
Limited partnerships number	62
Trading securities - mutual funds	261,000,000	246,000,000
Trading securities - equity securities	22,000,000	23,000,000
Trading securities - fixed maturities	7,000,000	7,000,000
Number of fixed maturities in an unrealized loss position	5,485
Total number of fixed maturities	26,258
Largest single unrealized loss in the fixed maturities	(3,000,000)
Number of equity securities in an unrealized loss position	93
Total number of equity securities	282
Largest single unrealized loss in the equity securities	(1,000,000)
Restricted assets in fixed maturities and short-term investments	16,300,000,000
Restricted assets in cash	$ 117,000,000	$ 162,000,000