Subsidiary Information (Details) (USD $)	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Assets
Total investment portfolio and cash	$ 11,345,900,000	$ 10,837,100,000		$ 11,012,500,000
Premiums receivable, net of ceding commissions payable	1,059,461,000	1,167,587,000	1,311,300,000	1,399,200,000
Ceded unearned premium reserve	773,321,000	821,819,000		1,080,500,000
Deferred acquisition costs	232,311,000	239,805,000		242,000,000
Reinsurance recoverable on unpaid losses	26,025,000	22,255,000		14,100,000
Credit derivative assets	603,867,000	592,898,000		492,500,000
Deferred tax asset, net	1,012,011,000	1,223,958,000		1,158,200,000
Financial guaranty variable interest entities' assets, at fair value	3,492,204,000	3,657,481,000		762,300,000
Other assets	693,800,000	1,231,600,000		622,400,000
Total assets	19,238,864,000	19,794,584,000		16,802,700,000
Liabilities and shareholders' equity
Unearned premium reserves	6,315,362,000	6,972,894,000		8,400,200,000
Loss and LAE reserve	518,145,000	562,955,000		289,500,000
Long-term debt	1,046,382,000	1,052,936,000		1,066,500,000
Credit derivative liabilities	2,788,200,000	2,465,520,000		2,034,600,000
Financial guaranty variable interest entities' liabilities, at fair value	4,037,600,000	4,264,200,000		762,700,000
Other liabilities	583,200,000	677,300,000		729,100,000
Total liabilities	15,288,879,000	15,995,820,000		13,282,600,000
Shareholders' equity attributable to Assured Guaranty Ltd.	3,950,000,000	3,798,800,000		3,520,500,000
Noncontrolling interest of financial guaranty variable interest entities				(400,000)
Total shareholders' equity	3,949,985,000	3,798,764,000		3,520,100,000
Total liabilities and shareholders' equity	19,238,864,000	19,794,584,000		16,802,700,000
Total Shareholders' Equity Attributable to Assured Guaranty Ltd.
Assets
Total investment portfolio and cash	16,000,000	22,500,000		52,500,000
Investment in subsidiaries	3,921,400,000	3,768,900,000		3,457,100,000
Other assets	23,800,000	19,200,000		22,600,000
Total assets	3,961,200,000	3,810,600,000		3,532,200,000
Liabilities and shareholders' equity
Other liabilities	11,200,000	11,800,000		11,700,000
Total liabilities	11,200,000	11,800,000		11,700,000
Shareholders' equity attributable to Assured Guaranty Ltd.	3,950,000,000	3,798,800,000		3,520,500,000
Total shareholders' equity	3,950,000,000	3,798,800,000		3,520,500,000
Total liabilities and shareholders' equity	3,961,200,000	3,810,600,000		3,532,200,000
AGUS (Issuer)
Assets
Total investment portfolio and cash	22,200,000	15,700,000		3,700,000
Investment in subsidiaries	3,210,000,000	3,030,700,000		2,852,000,000
Deferred tax asset, net	(600,000)	(800,000)		(400,000)
Other assets	21,700,000	3,800,000		1,300,000
Total assets	3,253,300,000	3,049,400,000		2,856,600,000
Liabilities and shareholders' equity
Long-term debt	518,900,000	518,400,000		517,400,000
Credit derivative liabilities	200,000	200,000		200,000
Other liabilities	2,800,000	(24,300,000)		(15,600,000)
Total liabilities	521,900,000	494,300,000		502,000,000
Shareholders' equity attributable to Assured Guaranty Ltd.	2,731,400,000	2,555,100,000		2,354,600,000
Total shareholders' equity	2,731,400,000	2,555,100,000		2,354,600,000
Total liabilities and shareholders' equity	3,253,300,000	3,049,400,000		2,856,600,000
AGMH (Issuer)
Assets
Total investment portfolio and cash	57,900,000	45,700,000		45,500,000
Investment in subsidiaries	2,714,300,000	2,378,800,000		2,070,900,000
Deferred tax asset, net	(94,600,000)	(95,800,000)		(97,900,000)
Other assets	37,200,000	15,200,000		34,500,000
Total assets	2,714,800,000	2,343,900,000		2,053,000,000
Liabilities and shareholders' equity
Long-term debt	411,300,000	407,500,000		400,000,000
Other liabilities	17,200,000	(6,900,000)		32,400,000
Total liabilities	428,500,000	400,600,000		432,400,000
Shareholders' equity attributable to Assured Guaranty Ltd.	2,286,300,000	1,943,300,000		1,620,600,000
Total shareholders' equity	2,286,300,000	1,943,300,000		1,620,600,000
Total liabilities and shareholders' equity	2,714,800,000	2,343,900,000		2,053,000,000
Other Subsidiaries
Assets
Total investment portfolio and cash	11,249,800,000	10,753,200,000		10,910,800,000
Investment in subsidiaries	2,731,400,000	2,555,100,000		2,354,600,000
Premiums receivable, net of ceding commissions payable	1,193,200,000	1,346,800,000		1,583,300,000
Ceded unearned premium reserve	1,802,600,000	1,883,400,000		1,972,900,000
Deferred acquisition costs	331,600,000	350,400,000		360,200,000
Reinsurance recoverable on unpaid losses	114,900,000	93,100,000		65,300,000
Credit derivative assets	669,200,000	672,700,000		540,000,000
Deferred tax asset, net	1,110,800,000	1,320,200,000		1,245,100,000
Intercompany receivable	300,000,000	300,000,000		300,000,000
Financial guaranty variable interest entities' assets, at fair value	3,492,200,000	3,657,500,000		762,300,000
Other assets	719,100,000	1,354,500,000		700,800,000
Total assets	23,714,800,000	24,286,900,000		20,795,300,000
Liabilities and shareholders' equity
Unearned premium reserves	7,289,900,000	7,976,500,000		9,221,400,000
Loss and LAE reserve	625,000,000	652,500,000		368,800,000
Long-term debt	116,200,000	127,000,000		149,100,000
Intercompany payable	300,000,000	300,000,000		300,000,000
Credit derivative liabilities	2,853,400,000	2,545,200,000		2,081,800,000
Financial guaranty variable interest entities' liabilities, at fair value	4,037,600,000	4,264,200,000		762,700,000
Other liabilities	780,700,000	1,023,700,000		979,700,000
Total liabilities	16,002,800,000	16,889,100,000		13,863,500,000
Shareholders' equity attributable to Assured Guaranty Ltd.	7,712,000,000	7,397,800,000		6,932,200,000
Noncontrolling interest of financial guaranty variable interest entities				(400,000)
Total shareholders' equity	7,712,000,000	7,397,800,000		6,931,800,000
Total liabilities and shareholders' equity	23,714,800,000	24,286,900,000		20,795,300,000
Consolidating Adjustments
Assets
Investment in subsidiaries	(12,577,100,000)	(11,733,500,000)		(10,734,600,000)
Premiums receivable, net of ceding commissions payable	(133,700,000)	(179,200,000)		(165,100,000)
Ceded unearned premium reserve	(1,029,300,000)	(1,061,600,000)		(892,400,000)
Deferred acquisition costs	(99,300,000)	(110,600,000)		(118,200,000)
Reinsurance recoverable on unpaid losses	(88,900,000)	(70,800,000)		(51,200,000)
Credit derivative assets	(65,300,000)	(79,800,000)		(47,500,000)
Deferred tax asset, net	(3,600,000)	400,000		11,400,000
Intercompany receivable	(300,000,000)	(300,000,000)		(300,000,000)
Other assets	(108,000,000)	(161,100,000)		(136,800,000)
Total assets	(14,405,200,000)	(13,696,200,000)		(12,434,400,000)
Liabilities and shareholders' equity
Unearned premium reserves	(974,500,000)	(1,003,600,000)		(821,200,000)
Loss and LAE reserve	(106,900,000)	(89,500,000)		(79,300,000)
Intercompany payable	(300,000,000)	(300,000,000)		(300,000,000)
Credit derivative liabilities	(65,400,000)	(79,900,000)		(47,400,000)
Other liabilities	(228,700,000)	(327,000,000)		(279,100,000)
Total liabilities	(1,675,500,000)	(1,800,000,000)		(1,527,000,000)
Shareholders' equity attributable to Assured Guaranty Ltd.	(12,729,700,000)	(11,896,200,000)		(10,907,400,000)
Total shareholders' equity	(12,729,700,000)	(11,896,200,000)		(10,907,400,000)
Total liabilities and shareholders' equity	$ (14,405,200,000)	$ (13,696,200,000)		$ (12,434,400,000)