Subsidiary Information (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012	Jun. 30, 2012		Dec. 31, 2011
Assets
Total investment portfolio and cash	$ 10,780		$ 11,223
Investment in subsidiaries	0		0
Premiums receivable, net of ceding commissions payable	915	[1]	1,005	964	[1]	1,003
Ceded unearned premium reserve	510		561
Deferred acquisition costs	125		116
Reinsurance recoverable on unpaid losses	60		58
Credit derivative assets	101		141
Deferred tax asset, net	850		721
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	2,674		2,688
Other	593		729
Total assets	16,608		17,242
Liabilities and shareholders’ equity
Unearned premium reserve	4,812		5,207
Loss and loss adjustment expense reserve	564		601
Long-term debt	827		836
Intercompany payable	0		0
Credit derivative liabilities	2,349		1,934
Financial guaranty variable interest entities’ liabilities, at fair value	3,074		3,141
Other	498		529
Total liabilities	12,124		12,248
Total Shareholders' Equity	4,484		4,994
Total liabilities and shareholders’ equity	16,608		17,242
Assured Guaranty Ltd. (Parent)
Assets
Total investment portfolio and cash	48		245
Investment in subsidiaries	4,414		4,734
Premiums receivable, net of ceding commissions payable	0		0
Ceded unearned premium reserve	0		0
Deferred acquisition costs	0		0
Reinsurance recoverable on unpaid losses	0		0
Credit derivative assets	0		0
Deferred tax asset, net	0		0
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	28		23
Total assets	4,490		5,002
Liabilities and shareholders’ equity
Unearned premium reserve	0		0
Loss and loss adjustment expense reserve	0		0
Long-term debt	0		0
Intercompany payable	0		0
Credit derivative liabilities	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	6		8
Total liabilities	6		8
Total Shareholders' Equity	4,484		4,994
Total liabilities and shareholders’ equity	4,490		5,002
AGUS (Issuer)
Assets
Total investment portfolio and cash	58		15
Investment in subsidiaries	3,867		3,958
Premiums receivable, net of ceding commissions payable	0		0
Ceded unearned premium reserve	0		0
Deferred acquisition costs	0		0
Reinsurance recoverable on unpaid losses	0		0
Credit derivative assets	0		0
Deferred tax asset, net	48		48
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	34		29
Total assets	4,007		4,050
Liabilities and shareholders’ equity
Unearned premium reserve	0		0
Loss and loss adjustment expense reserve	0		0
Long-term debt	347		347
Intercompany payable	173		173
Credit derivative liabilities	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	9		6
Total liabilities	529		526
Total Shareholders' Equity	3,478		3,524
Total liabilities and shareholders’ equity	4,007		4,050
AGMH (Issuer)
Assets
Total investment portfolio and cash	31		30
Investment in subsidiaries	3,417		3,225
Premiums receivable, net of ceding commissions payable	0		0
Ceded unearned premium reserve	0		0
Deferred acquisition costs	0		0
Reinsurance recoverable on unpaid losses	0		0
Credit derivative assets	0		0
Deferred tax asset, net	(91)		(94)
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	34		26
Total assets	3,391		3,187
Liabilities and shareholders’ equity
Unearned premium reserve	0		0
Loss and loss adjustment expense reserve	0		0
Long-term debt	427		423
Intercompany payable	0		0
Credit derivative liabilities	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	15		15
Total liabilities	442		438
Total Shareholders' Equity	2,949		2,749
Total liabilities and shareholders’ equity	3,391		3,187
Other Subsidiaries
Assets
Total investment portfolio and cash	10,943		11,233
Investment in subsidiaries	0		3,524
Premiums receivable, net of ceding commissions payable	1,044		1,147
Ceded unearned premium reserve	1,441		1,550
Deferred acquisition costs	206		190
Reinsurance recoverable on unpaid losses	201		223
Credit derivative assets	595		553
Deferred tax asset, net	916		789
Intercompany receivable	173		173
Financial guaranty variable interest entities’ assets, at fair value	2,674		2,688
Other	669		816
Total assets	18,862		22,886
Liabilities and shareholders’ equity
Unearned premium reserve	5,718		6,168
Loss and loss adjustment expense reserve	721		778
Long-term debt	53		66
Intercompany payable	300		300
Credit derivative liabilities	2,843		2,346
Financial guaranty variable interest entities’ liabilities, at fair value	3,074		3,141
Other	764		803
Total liabilities	13,473		13,602
Total Shareholders' Equity	5,389		9,284
Total liabilities and shareholders’ equity	18,862		22,886
Consolidating Adjustments
Assets
Total investment portfolio and cash	(300)		(300)
Investment in subsidiaries	(11,698)		(15,441)
Premiums receivable, net of ceding commissions payable	(129)		(142)
Ceded unearned premium reserve	(931)		(989)
Deferred acquisition costs	(81)		(74)
Reinsurance recoverable on unpaid losses	(141)		(165)
Credit derivative assets	(494)		(412)
Deferred tax asset, net	(23)		(22)
Intercompany receivable	(173)		(173)
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	(172)		(165)
Total assets	(14,142)		(17,883)
Liabilities and shareholders’ equity
Unearned premium reserve	(906)		(961)
Loss and loss adjustment expense reserve	(157)		(177)
Long-term debt	0		0
Intercompany payable	(473)		(473)
Credit derivative liabilities	(494)		(412)
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	(296)		(303)
Total liabilities	(2,326)		(2,326)
Total Shareholders' Equity	(11,816)		(15,557)
Total liabilities and shareholders’ equity	$ (14,142)		$ (17,883)

[1] Excludes $20 million and $32 million as of June 30, 2013 and June 30, 2012, respectively, related to consolidated FG VIEs.