Reinsurance and Other Monoline Exposures (Details 2) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	$ 30,092	[1]
Ceded Par Outstanding	23,646
Assumed Par Outstanding	35,940
Ceded par outstanding related to insured credit derivatives	3,415
Assumed Premium Receivable, net of Commissions	93
Ceded Premium Payable, net of Commissions	(141)
Assumed Expected Loss and LAE	(158)
Ceded Expected Loss and LAE	62
National Public Finance Guarantee Corporation
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Fixed maturity securities wrapped by monoline reinsurer	557
American Overseas Reinsurance Company Limited (f/k/a Ram Re)
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	8,971	[1],[2]
Ceded Par Outstanding	0	[2]
Assumed Par Outstanding	30	[2]
Assumed Premium Receivable, net of Commissions	0
Ceded Premium Payable, net of Commissions	(11)
Assumed Expected Loss and LAE	0
Ceded Expected Loss and LAE	8
Tokio Marine & Nichido Fire Insurance Co., Ltd.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	7,634	[1]
Ceded Par Outstanding	0
Assumed Par Outstanding	0
Assumed Premium Receivable, net of Commissions	0
Ceded Premium Payable, net of Commissions	(23)
Assumed Expected Loss and LAE	0
Ceded Expected Loss and LAE	37
Radian Asset Assurance Inc.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	4,897	[1]
Ceded Par Outstanding	42
Assumed Par Outstanding	1,273
Assumed Premium Receivable, net of Commissions	0
Ceded Premium Payable, net of Commissions	(18)
Assumed Expected Loss and LAE	0
Ceded Expected Loss and LAE	1
Syncora Guarantee Inc.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	4,031	[1]
Ceded Par Outstanding	1,789
Assumed Par Outstanding	162
Assumed Premium Receivable, net of Commissions	0
Ceded Premium Payable, net of Commissions	(40)
Assumed Expected Loss and LAE	22
Ceded Expected Loss and LAE	1
Mitsui Sumitomo Insurance Co. Ltd.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	2,176	[1],[3]
Ceded Par Outstanding	0	[3]
Assumed Par Outstanding	0	[3]
Assumed Premium Receivable, net of Commissions	0
Ceded Premium Payable, net of Commissions	(4)
Assumed Expected Loss and LAE	0
Ceded Expected Loss and LAE	8
ACA Financial Guaranty Corp.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	819	[1]
Ceded Par Outstanding	6
Assumed Par Outstanding	10
Swiss Reinsurance Co.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	425	[1]
Ceded Par Outstanding	0
Assumed Par Outstanding	0
Assumed Premium Receivable, net of Commissions	0
Ceded Premium Payable, net of Commissions	(3)
Assumed Expected Loss and LAE	0
Ceded Expected Loss and LAE	2
Ambac Assurance Corporation
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Fixed maturity securities wrapped by monoline reinsurer	479
Ceded Par Amount	85	[1]
Ceded Par Outstanding	6,489
Assumed Par Outstanding	19,596
Assumed Premium Receivable, net of Commissions	71
Ceded Premium Payable, net of Commissions	0
Assumed Expected Loss and LAE	(71)
Ceded Expected Loss and LAE	0
CIFG Assurance North America Inc.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	61	[1]
Ceded Par Outstanding	255
Assumed Par Outstanding	5,331
Assumed Premium Receivable, net of Commissions	0
Ceded Premium Payable, net of Commissions	0
Assumed Expected Loss and LAE	0
Ceded Expected Loss and LAE	5
MBIA Inc.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	0	[1],[4]
Ceded Par Outstanding	10,498	[4]
Assumed Par Outstanding	7,726	[4]
Assumed Premium Receivable, net of Commissions	14
Ceded Premium Payable, net of Commissions	0
Assumed Expected Loss and LAE	(18)
Ceded Expected Loss and LAE	0
Financial Guaranty Insurance Co.
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Ceded Par Amount	0	[1]
Ceded Par Outstanding	2,634
Assumed Par Outstanding	1,766
Assumed Premium Receivable, net of Commissions	8
Ceded Premium Payable, net of Commissions	0
Assumed Expected Loss and LAE	(91)
Ceded Expected Loss and LAE	0
Other
Exposure, Premium Receivable, and Loss and LAE by Reinsurer
Fixed maturity securities wrapped by monoline reinsurer	28
Ceded Par Amount	993	[1]
Ceded Par Outstanding	1,933
Assumed Par Outstanding	46
Assumed Premium Receivable, net of Commissions	0
Ceded Premium Payable, net of Commissions	(42)
Assumed Expected Loss and LAE	0
Ceded Expected Loss and LAE	$ 0

[1] Includes $3,415 million in ceded par outstanding related to insured credit derivatives.

[2] Represents “Withdrawn Rating.”

[3] The Company has structural collateral agreements satisfying the triple-A credit requirement of S&P and/or Moody’s.

[4] MBIA Inc. includes various subsidiaries which are rated A and B by S&P and Baa1, B1, B3, WR and NR by Moody’s