Condensed Financial Information of Parent Company - Statements Of Cash Flows (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flows from Operating Activities
Net Income	$ 1,545	$ 1,678	$ 2,174
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Other, Net	52	(52)	(117)
Realized Investment Losses (Gains), Net	(193)	(288)	(426)
NET CASH PROVIDED BY OPERATING ACTIVITIES	2,299	1,878	2,331
Cash Flows from Investing Activities
Proceeds from Fixed Maturities Sales	2,271	1,730	2,287
Maturities, Calls and Redemptions	4,290	3,540	2,856
Proceeds from Sales of Equity Securities	160	167	129
Purchases of Fixed Maturities	(7,247)	(5,014)	(5,176)
Investments in Other Invested Assets, Net	293	285	173
Decrease (Increase) in Short Term Investments, Net	(629)	11	38
Other, Net			(6)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	(972)	580	67
Cash Flows from Financing Activities
Repayment of Long Term Debt		(400)
Proceeds from Issuance of Common Stock Under Stock-Based Employee Compensation Plans	74	80	74
Repurchase of Shares	(959)	(1,707)	(2,003)
Dividends Paid to Shareholders	(438)	(450)	(472)
NET CASH USED IN FINANCING ACTIVITIES	(1,335)	(2,470)	(2,379)
Net Increase in Cash	(8)	(12)	19
Cash at Beginning of Year	58	70	51
CASH AT END OF YEAR	50	58	70
Parent Company [Member]
Cash Flows from Operating Activities
Net Income	1,545	1,678	2,174
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Equity in Net Income of Consolidated Subsidiaries	(1,787)	(1,912)	(2,371)
Other, Net	57	(28)	(14)
Realized Investment Losses (Gains), Net	6	(9)	(16)
NET CASH PROVIDED BY OPERATING ACTIVITIES	(179)	(271)	(227)
Cash Flows from Investing Activities
Proceeds from Fixed Maturities Sales	24	2	3
Maturities, Calls and Redemptions	673	456	202
Proceeds from Sales of Equity Securities		9
Purchases of Fixed Maturities	(1,046)	(257)	(73)
Investments in Other Invested Assets, Net			33
Decrease (Increase) in Short Term Investments, Net	89	(219)	199
Dividends Received from Consolidated Insurance Subsidiaries	1,760	2,700	2,200
Distributions Received from Consolidated Non-Insurance Subsidiaries	1	1	4
Other, Net	1	56	60
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	1,502	2,748	2,628
Cash Flows from Financing Activities
Repayment of Long Term Debt		(400)
Proceeds from Issuance of Common Stock Under Stock-Based Employee Compensation Plans	74	80	74
Repurchase of Shares	(959)	(1,707)	(2,003)
Dividends Paid to Shareholders	(438)	(450)	(472)
NET CASH USED IN FINANCING ACTIVITIES	(1,323)	(2,477)	(2,401)
Net Increase in Cash
Cash at Beginning of Year
CASH AT END OF YEAR