Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	$ 18,228	$ 3,968
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(652.0)	(48.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	894	577
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(63.0)	(50.0)
Investment securities, Unrealized loss position, Total Fair Value	19,122	4,545
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(715.0)	(98.0)
U.S. Treasury and agency
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	1,794	440
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(57.0)	(1.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	31	0
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(6.0)	0
Investment securities, Unrealized loss position, Total Fair Value	1,825	440
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(63.0)	(1.0)
Foreign
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	4,621	1,234
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(114.0)	(8.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	201	88
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(8.0)	(6.0)
Investment securities, Unrealized loss position, Total Fair Value	4,822	1,322
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(122.0)	(14.0)
Corporate securities
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	3,836	1,026
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(118.0)	(23.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	194	85
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(14.0)	(8.0)
Investment securities, Unrealized loss position, Total Fair Value	4,030	1,111
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(132.0)	(31.0)
Mortgage backed-securities
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	5,248	855
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(197.0)	(4.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	384	356
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(31.0)	(32.0)
Investment securities, Unrealized loss position, Total Fair Value	5,632	1,211
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(228.0)	(36.0)
States, municipalities, and political subdivisions
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	2,164	316
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(90.0)	(3.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	84	48
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(4.0)	(4.0)
Investment securities, Unrealized loss position, Total Fair Value	2,248	364
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(94.0)	(7.0)
Total fixed maturities
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	17,663	3,871
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(576.0)	(39.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	894	577
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(63.0)	(50.0)
Investment securities, Unrealized loss position, Total Fair Value	18,557	4,448
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(639.0)	(89.0)
Equity securities
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	498	29
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(67.0)	(4.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	0
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	0
Investment securities, Unrealized loss position, Total Fair Value	498	29
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(67.0)	(4.0)
Other investments
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	67	68
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(9.0)	(5.0)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	0
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	0
Investment securities, Unrealized loss position, Total Fair Value	67	68
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	$ (9.0)	$ (5.0)