Subsidiary Information (Details 3) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Condensed financial statements
Net cash flows provided by (used in) operating activities	$ 614,434,000	$ (249,589,000)	$ 104,000,000	$ 279,200,000	$ 427,000,000
Fixed maturity securities:
Purchases	(1,349,745,000)	(1,166,379,000)	(2,461,700,000)	(2,287,700,000)	(1,272,000,000)
Sales	685,980,000	780,818,000	1,063,600,000	1,519,300,000	532,200,000
Maturities	326,927,000	488,552,000	994,400,000	217,900,000	11,700,000
Sales (purchases) of short-term investments, net	(38,676,000)	276,641,000	637,300,000	(397,100,000)	78,500,000
Net proceeds from financial guaranty variable entities' assets	423,977,000	217,329,000	424,000,000
Acquisition of AGMH				(459,000,000)
Other	8,696,000	8,317,000	19,700,000	9,400,000
Net cash flows provided by (used in) investing activities	57,159,000	605,278,000	677,300,000	(1,397,200,000)	(649,600,000)
Cash flows from financing activities
Net proceeds from issuance of common stock and equity units				1,190,100,000	249,000,000
Dividends paid	(16,577,000)	(16,613,000)	(33,200,000)	(22,300,000)	(16,000,000)
Repurchases of common stock		(10,457,000)	(10,500,000)	(3,700,000)
Share activity under option and incentive plans	(2,652,000)	(2,233,000)	(2,000,000)	(700,000)	(3,600,000)
Net paydowns of financial guaranty variable entities' liabilities	(593,294,000)	(259,367,000)	(650,800,000)
Payment of long-term debt	(10,294,000)	(10,850,000)	(20,900,000)	(14,800,000)
Net cash flows provided by (used in) financing activities	(622,817,000)	(299,520,000)	(717,400,000)	1,148,600,000	229,400,000
Effect of foriegn exchange rate changes	3,215,000	(3,090,000)	(800,000)	1,200,000	(2,500,000)
Increase (decrease) in cash	51,991,000	53,079,000	63,100,000	31,800,000	4,300,000
Cash at beginning of period	107,179,000	44,133,000	44,133,000	12,300,000	8,000,000
Cash at end of period	159,170,000	97,212,000	107,179,000	44,133,000	12,300,000
Total Shareholders' Equity Attributable to Assured Guaranty Ltd.
Condensed financial statements
Net cash flows provided by (used in) operating activities	12,700,000	(2,100,000)	15,700,000	19,600,000	21,400,000
Fixed maturity securities:
Sales (purchases) of short-term investments, net	6,500,000	31,500,000	30,000,000	(52,300,000)	200,000
Capital contribution to subsidiary				(962,900,000)	(250,000,000)
Net cash flows provided by (used in) investing activities	6,500,000	31,500,000	30,000,000	(1,015,200,000)	(249,800,000)
Cash flows from financing activities
Net proceeds from issuance of common stock and equity units				1,022,800,000	249,000,000
Dividends paid	(16,600,000)	(16,600,000)	(33,200,000)	(22,800,000)	(17,000,000)
Repurchases of common stock		(10,500,000)	(10,500,000)	(3,700,000)
Share activity under option and incentive plans	(2,600,000)	(2,300,000)	(2,000,000)	(700,000)	(3,600,000)
Net cash flows provided by (used in) financing activities	(19,200,000)	(29,400,000)	(45,700,000)	995,600,000	228,400,000
AGUS (Issuer)
Condensed financial statements
Net cash flows provided by (used in) operating activities	6,600,000	10,700,000	11,800,000	(23,900,000)	(5,200,000)
Fixed maturity securities:
Sales (purchases) of short-term investments, net	(17,300,000)	(10,800,000)	1,100,000	(3,500,000)	5,200,000
Capital contribution to subsidiary				(556,700,000)	(100,000,000)
Acquisition of AGMH				(546,000,000)
Net cash flows provided by (used in) investing activities	(17,300,000)	(10,800,000)	1,100,000	(1,106,200,000)	(94,800,000)
Cash flows from financing activities
Net proceeds from issuance of common stock and equity units				167,300,000
Capital contribution from parent				962,900,000	100,000,000
Net cash flows provided by (used in) financing activities				1,130,200,000	100,000,000
Increase (decrease) in cash	(10,700,000)	(100,000)	12,900,000	100,000
Cash at beginning of period	13,000,000	100,000	100,000
Cash at end of period	2,300,000		13,000,000	100,000
AGMH (Issuer)
Condensed financial statements
Net cash flows provided by (used in) operating activities	(21,700,000)	(25,100,000)	(49,000,000)	(24,700,000)
Fixed maturity securities:
Purchases	(300,000)		(15,000,000)	(1,700,000)
Sales			4,500,000
Maturities	400,000	4,100,000	6,400,000	1,600,000
Sales (purchases) of short-term investments, net	(12,100,000)	(2,400,000)	3,100,000	(300,000)
Investment in subsidiary	25,000,000	25,000,000	50,000,000	25,000,000
Other	8,700,000
Net cash flows provided by (used in) investing activities	21,700,000	26,700,000	49,000,000	24,600,000
Cash flows from financing activities
Increase (decrease) in cash		1,600,000		(100,000)
Cash at beginning of period				100,000
Cash at end of period		1,600,000
Other Subsidiaries
Condensed financial statements
Net cash flows provided by (used in) operating activities	650,800,000	(203,000,000)	199,500,000	355,800,000	459,600,000
Fixed maturity securities:
Purchases	(1,349,400,000)	(1,166,300,000)	(2,446,700,000)	(2,286,000,000)	(1,272,000,000)
Sales	686,000,000	780,800,000	1,059,100,000	1,519,300,000	532,200,000
Maturities	326,500,000	484,500,000	988,000,000	216,300,000	11,700,000
Sales (purchases) of short-term investments, net	(15,800,000)	258,300,000	603,100,000	(341,000,000)	73,100,000
Net proceeds from financial guaranty variable entities' assets	424,000,000	217,300,000	424,000,000
Capital contribution to subsidiary				(512,000,000)
Acquisition of AGMH				87,000,000
Other		8,300,000	19,700,000	9,400,000
Net cash flows provided by (used in) investing activities	71,300,000	582,900,000	647,200,000	(1,307,000,000)	(655,000,000)
Cash flows from financing activities
Capital contribution from parent				1,068,700,000	250,000,000
Return of capital	(25,000,000)	(25,000,000)	(50,000,000)	(25,000,000)
Dividends paid	(34,000,000)	(30,000,000)	(74,000,000)	(47,100,000)	(47,800,000)
Net paydowns of financial guaranty variable entities' liabilities	(593,300,000)	(259,400,000)	(650,800,000)
Payment of long-term debt	(10,300,000)	(10,800,000)	(20,900,000)	(14,800,000)
Net cash flows provided by (used in) financing activities	(662,600,000)	(325,200,000)	(795,700,000)	981,800,000	202,200,000
Effect of foriegn exchange rate changes	3,200,000	(3,100,000)	(800,000)	1,200,000	(2,500,000)
Increase (decrease) in cash	62,700,000	51,600,000	50,200,000	31,800,000	4,300,000
Cash at beginning of period	94,200,000	44,000,000	44,000,000	12,300,000	8,000,000
Cash at end of period	156,900,000	95,600,000	94,200,000	44,000,000	12,300,000
Consolidating Adjustments
Condensed financial statements
Net cash flows provided by (used in) operating activities	(34,000,000)	(30,000,000)	(74,000,000)	(47,600,000)	(48,800,000)
Fixed maturity securities:
Capital contribution to subsidiary				2,031,600,000	350,000,000
Investment in subsidiary	(25,000,000)	(25,000,000)	(50,000,000)	(25,000,000)
Net cash flows provided by (used in) investing activities	(25,000,000)	(25,000,000)	(50,000,000)	2,006,600,000	350,000,000
Cash flows from financing activities
Capital contribution from parent				(2,031,600,000)	(350,000,000)
Return of capital	25,000,000	25,000,000	50,000,000	25,000,000
Dividends paid	34,000,000	30,000,000	74,000,000	47,600,000	48,800,000
Net cash flows provided by (used in) financing activities	$ 59,000,000	$ 55,000,000	$ 124,000,000	$ (1,959,000,000)	$ (301,200,000)