Subsidiary Information (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011		Dec. 31, 2011	Dec. 31, 2010
Condensed financial statements
Repurchases of common stock	$ (24,313,000)	$ 0
Assets
Total investment portfolio and cash	11,497,000,000			11,313,300,000
Premiums receivable, net of ceding commissions payable	964,063,000	1,059,500,000	[1]	1,002,852,000	1,167,600,000
Ceded unearned premium reserve	590,781,000			708,872,000
Deferred acquisition costs	126,755,000			132,418,000
Reinsurance recoverable on unpaid losses	170,495,000			69,300,000
Credit derivative assets	429,900,000			468,900,000
Deferred tax asset, net	815,084,000			803,529,000
Financial guaranty variable interest entities' assets, at fair value	2,725,979,000			2,819,077,000
Other	754,300,000			706,400,000
Total assets	18,074,464,000			18,024,660,000
Liabilities and shareholders' equity
Unearned premium reserves	5,583,380,000			5,962,799,000
Loss and loss adjustment expense reserve	995,217,000			679,011,000
Long-term debt	846,354,000			1,038,302,000
Credit derivative liabilities	2,095,900,000			1,772,800,000
Financial guaranty variable interest entities' liabilities, at fair value	3,281,300,000			3,458,400,000
Other	548,200,000			461,800,000
Total liabilities	13,350,398,000			13,373,095,000
Total shareholders' equity	4,724,066,000			4,651,565,000
Total liabilities and shareholders' equity	18,074,464,000			18,024,660,000
Assured Guaranty Ltd. (Parent)
Condensed financial statements
Repurchases of common stock	(24,300,000)
Assets
Total investment portfolio and cash	214,900,000			32,900,000
Investment in subsidiaries	4,503,900,000			4,606,700,000
Other	26,500,000			23,100,000
Total assets	4,745,300,000			4,662,700,000
Liabilities and shareholders' equity
Other	21,200,000			11,100,000
Total liabilities	21,200,000			11,100,000
Total shareholders' equity	4,724,100,000			4,651,600,000
Total liabilities and shareholders' equity	4,745,300,000			4,662,700,000
AGUS (Issuer)
Assets
Total investment portfolio and cash	33,300,000			99,500,000
Investment in subsidiaries	3,738,100,000			3,730,000,000
Deferred tax asset, net	22,500,000			22,500,000
Other	24,800,000			(71,300,000)
Total assets	3,818,700,000			3,780,700,000
Liabilities and shareholders' equity
Long-term debt	347,500,000			519,500,000
Intercompany payable	172,500,000
Credit derivative liabilities	200,000			200,000
Other	2,300,000			2,900,000
Total liabilities	522,500,000			522,600,000
Total shareholders' equity	3,296,200,000			3,258,100,000
Total liabilities and shareholders' equity	3,818,700,000			3,780,700,000
AGMH (Issuer)
Assets
Total investment portfolio and cash	52,900,000			61,400,000
Investment in subsidiaries	2,915,400,000			2,801,300,000
Deferred tax asset, net	(75,800,000)			(76,900,000)
Other	17,800,000			26,900,000
Total assets	2,910,300,000			2,812,700,000
Liabilities and shareholders' equity
Long-term debt	418,900,000			415,100,000
Other	15,800,000			15,700,000
Total liabilities	434,700,000			430,800,000
Total shareholders' equity	2,475,600,000			2,381,900,000
Total liabilities and shareholders' equity	2,910,300,000			2,812,700,000
Other Subsidiaries
Assets
Total investment portfolio and cash	11,195,900,000			11,119,500,000
Investment in subsidiaries	3,296,200,000			3,258,100,000
Premiums receivable, net of ceding commissions payable	1,099,100,000			1,149,600,000
Ceded unearned premium reserve	1,601,000,000			1,739,100,000
Deferred acquisition costs	209,500,000			223,300,000
Reinsurance recoverable on unpaid losses	421,800,000			211,800,000
Credit derivative assets	508,500,000			503,400,000
Deferred tax asset, net	882,300,000			867,200,000
Intercompany receivable	472,500,000			300,000,000
Financial guaranty variable interest entities' assets, at fair value	2,726,000,000			2,819,100,000
Other	854,000,000			836,500,000
Total assets	23,266,800,000			23,027,600,000
Liabilities and shareholders' equity
Unearned premium reserves	6,558,000,000			6,949,400,000
Loss and loss adjustment expense reserve	1,257,400,000			834,200,000
Long-term debt	80,000,000			103,700,000
Intercompany payable	300,000,000			300,000,000
Credit derivative liabilities	2,173,800,000			1,807,100,000
Financial guaranty variable interest entities' liabilities, at fair value	3,281,300,000			3,458,400,000
Other	802,700,000			674,700,000
Total liabilities	14,453,200,000			14,127,500,000
Total shareholders' equity	8,813,600,000			8,900,100,000
Total liabilities and shareholders' equity	23,266,800,000			23,027,600,000
Consolidating Adjustments
Assets
Total investment portfolio and cash	0			0
Investment in subsidiaries	(14,453,600,000)			(14,396,100,000)
Premiums receivable, net of ceding commissions payable	(135,000,000)			(146,700,000)
Ceded unearned premium reserve	(1,010,200,000)			(1,030,200,000)
Deferred acquisition costs	(82,700,000)			(90,900,000)
Reinsurance recoverable on unpaid losses	(251,300,000)			(142,500,000)
Credit derivative assets	(78,600,000)			(34,500,000)
Deferred tax asset, net	(13,900,000)			(9,300,000)
Intercompany receivable	(472,500,000)			(300,000,000)
Financial guaranty variable interest entities' assets, at fair value	0			0
Other	(168,800,000)			(108,800,000)
Total assets	(16,666,600,000)			(16,259,000,000)
Liabilities and shareholders' equity
Unearned premium reserves	(974,600,000)			(986,600,000)
Loss and loss adjustment expense reserve	(262,200,000)			(155,200,000)
Long-term debt	0			0
Intercompany payable	(472,500,000)			(300,000,000)
Credit derivative liabilities	(78,100,000)			(34,500,000)
Financial guaranty variable interest entities' liabilities, at fair value	0			0
Other	(293,800,000)			(242,600,000)
Total liabilities	(2,081,200,000)			(1,718,900,000)
Total shareholders' equity	(14,585,400,000)			(14,540,100,000)
Total liabilities and shareholders' equity	$ (16,666,600,000)			$ (16,259,000,000)

[1] Excludes $31.7 million and $31.7 million as of June 30, 2012 and 2011, respectively, related to consolidated FG VIEs.