Debt (Long-Term Debt) (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Jan. 16, 2008	Dec. 31, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Long-term debt, gross		$ 723		$ 901
Less unamortized discount		1		1
Subtotal		722		900
Non Variable Interest Entities [Member]
Debt Instrument [Line Items]
Total		1,662		1,840
6.400% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate		6.40%
Long-term debt, maturity, year		2022
Initial Callable date		Aug. 15, 2006
6.400% Senior Notes Due 2022 [Member] | Non Variable Interest Entities [Member]
Debt Instrument [Line Items]
Long-term debt, gross		269	[1]	275	[1]
7.000% Debentures Due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate		7.00%
Long-term debt, maturity, year		2025
7.000% Debentures Due 2025 [Member] | Non Variable Interest Entities [Member]
Debt Instrument [Line Items]
Long-term debt, gross		56		56
7.150% Debentures Due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate		7.15%
Long-term debt, maturity, year		2027
7.150% Debentures Due 2027 [Member] | Non Variable Interest Entities [Member]
Debt Instrument [Line Items]
Long-term debt, gross		100		100
6.625% Debentures Due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate		6.625%
Long-term debt, maturity, year		2028
6.625% Debentures Due 2028 [Member] | Non Variable Interest Entities [Member]
Debt Instrument [Line Items]
Long-term debt, gross		141		141
5.700% Senior Notes Due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt, interest rate		5.70%
Long-term debt, maturity, year		2034
5.700% Senior Notes Due 2034 [Member] | Non Variable Interest Entities [Member]
Debt Instrument [Line Items]
Long-term debt, gross		157	[2]	329	[2]
14% Surplus Notes Due 2033 [Member]
Debt Instrument [Line Items]
14% Surplus Notes due 2033	1,000	940	[3]	940	[3]
Long-term debt, interest rate	14.00%	14.00%
Long-term debt, maturity, year		2033
Initial Callable date		Jan. 15, 2018
Callable date for fifth anniversary of initial callable date		January 15, 2018
Callable date for subsequent fifth anniversary of initial callable date		January 15, 2023
Latest callable date before maturity		Jan. 15, 2028
Long-term debt, maturity date	Jan. 15, 2033	Jan. 15, 2033
14% Surplus Notes Due 2033 [Member] | Non Variable Interest Entities [Member]
Debt Instrument [Line Items]
14% Surplus Notes due 2033		$ 940		$ 940

[1] Callable on or after August 15, 2006 at 100.00.

[2] Callable anytime at the greater of 100.00 or the present value of the remaining scheduled payments of principal and interest.

[3] Callable on or after January 15, 2018 and every fifth anniversary thereafter at 100.00.