Debt (Narrative) (Details) (USD $)	12 Months Ended		12 Months Ended		12 Months Ended		0 Months Ended	12 Months Ended									12 Months Ended
	Dec. 31, 2011 days	Dec. 31, 2010	Dec. 31, 2011 Cutwater-ISC [Member]	Dec. 31, 2010 Cutwater-ISC [Member]	Dec. 31, 2011 Triple-A-One Funding, LLC [Member]	Dec. 31, 2010 Triple-A-One Funding, LLC [Member]	Jan. 16, 2008 14% Surplus Notes Due 2033 [Member]	Dec. 31, 2011 14% Surplus Notes Due 2033 [Member]	Dec. 31, 2011 Investment Agreement Obligations [Member]	Dec. 31, 2010 Investment Agreement Obligations [Member]	Dec. 31, 2011 Medium-Term Notes [Member]	Dec. 31, 2010 Medium-Term Notes [Member]	Dec. 31, 2011 Non Variable Interest Entities [Member] 14% Surplus Notes Due 2033 [Member]		Dec. 31, 2010 Non Variable Interest Entities [Member] 14% Surplus Notes Due 2033 [Member]		Dec. 31, 2011 Variable Interest Entities [Member]	Dec. 31, 2010 Variable Interest Entities [Member]
Debt Instrument [Line Items]
Aggregate principal amount in excess of stated amount	$ 10,000,000	$ 10,000,000
Long-term debt, interest rate							14.00%	14.00%
Long-term debt, maturity date							Jan. 15, 2033	Jan. 15, 2033
Interest rate terms					one-month LIBOR plus 0.75%	one-month LIBOR plus 0.75%	interest rate of 14% until January 15, 2013 and thereafter at an interest rate of three-month LIBOR plus 11.26%.
Surplus notes outstanding							1,000,000,000						940,000,000	[1]	945,000,000	[1]
Surplus notes purchased at par value	5,000,000
Surplus notes, cost of par value, percentage	55.00%
Surplus notes repurchased at outstanding par value	47,000,000
Surplus notes, weighted average price per unit	$ 77.08
Annual interest rates, minimum									0.00%	0.00%	0.00%	0.00%					0.64%	0.52%
Annual interest rates, maximum									7.38%	7.38%	8.68%	8.37%					1.78%	1.76%
Weighted average interest rate									4.31%	3.73%	3.19%	3.17%					1.41%	1.37%
Outstanding letters of credit			10,000,000
Number of pooled investment programs			2
Maximum amount of future payments under commitments			3,300,000,000	4,200,000,000
Triple-A One commercial paper maturity, days	270
Covering of the face amount of commercial paper outstanding, percentage					100.00%
Repaid value in full and borrowings under liquidity facilities					$ 360,000,000
Expected debt facilities fully repaid					2037

[1] Callable on January 15, 2013 and every fifth anniversary thereafter at 100.00.