Subsidiary Information (Details 2) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues
Net earned premiums	$ 219,299,000	$ 230,068,000	$ 412,976,000	$ 484,045,000
Net investment income	101,588,000	102,591,000	199,350,000	200,003,000
Net realized investment gains (losses)	(3,156,000)	(5,090,000)	(1,840,000)	(2,284,000)
Net change in fair value of credit derivatives:
Realized Gains and Other Settlements	(22,664,000)	(10,836,000)	(79,545,000)	24,591,000
Unrealized Gains (Losses)	283,327,000	(54,059,000)	(350,431,000)	(325,695,000)
Net change in fair value of credit derivatives	260,663,000	(64,895,000)	(429,976,000)	(301,104,000)
Other	181,000,000	(146,400,000)	221,500,000	14,600,000
Total revenues	759,498,000	116,294,000	402,092,000	395,207,000
Expenses
Loss and loss adjustment expenses	122,446,000	123,913,000	369,293,000	98,333,000
Amortization of deferred acquisition costs	4,526,000	5,810,000	9,939,000	9,472,000
Interest expense	25,426,000	24,696,000	50,099,000	49,456,000
Other operating expenses	53,447,000	53,249,000	114,727,000	116,132,000
Total expenses	205,845,000	207,668,000	544,058,000	273,393,000
Income (loss) before income taxes	553,653,000	(91,374,000)	(141,966,000)	121,814,000
Total provision (benefit) for income taxes	177,105,000	(48,269,000)	(35,490,000)	25,663,000
Net income (loss)	376,548,000	(43,105,000)	(106,476,000)	96,151,000
Comprehensive income (loss)	407,503,000	76,173,000	(44,633,000)	189,993,000
Assured Guaranty Ltd. (Parent)
Net change in fair value of credit derivatives:
Equity in earnings of subsidiaries	381,700,000	(37,700,000)	(94,800,000)	110,000,000
Total revenues	381,700,000	(37,700,000)	(94,800,000)	110,000,000
Expenses
Other operating expenses	5,200,000	5,400,000	11,700,000	13,800,000
Total expenses	5,200,000	5,400,000	11,700,000	13,800,000
Income (loss) before income taxes	376,500,000	(43,100,000)	(106,500,000)	96,200,000
Net income (loss)	376,500,000	(43,100,000)	(106,500,000)	96,200,000
Comprehensive income (loss)	407,500,000	76,100,000	(44,600,000)	190,000,000
AGUS (Issuer)
Net change in fair value of credit derivatives:
Equity in earnings of subsidiaries	360,500,000	(46,500,000)	7,200,000	128,600,000
Total revenues	360,500,000	(46,500,000)	7,200,000	128,600,000
Expenses
Interest expense	9,900,000	9,900,000	19,800,000	19,700,000
Other operating expenses	600,000	100,000	1,000,000	300,000
Total expenses	10,500,000	10,000,000	20,800,000	20,000,000
Income (loss) before income taxes	350,000,000	(56,500,000)	(13,600,000)	108,600,000
Total provision (benefit) for income taxes	(3,700,000)	(3,500,000)	(7,300,000)	(7,000,000)
Net income (loss)	353,700,000	(53,000,000)	(6,300,000)	115,600,000
Comprehensive income (loss)	372,900,000	52,100,000	38,000,000	202,900,000
AGMH (Issuer)
Revenues
Net investment income	300,000	100,000	600,000	300,000
Net change in fair value of credit derivatives:
Equity in earnings of subsidiaries	168,300,000	45,000,000	161,800,000	336,600,000
Total revenues	168,600,000	45,100,000	162,400,000	336,900,000
Expenses
Interest expense	13,400,000	13,400,000	26,800,000	26,800,000
Other operating expenses	200,000	200,000	400,000	700,000
Total expenses	13,600,000	13,600,000	27,200,000	27,500,000
Income (loss) before income taxes	155,000,000	31,500,000	135,200,000	309,400,000
Total provision (benefit) for income taxes	2,900,000	(4,700,000)	(9,300,000)	(9,500,000)
Net income (loss)	152,100,000	36,200,000	144,500,000	318,900,000
Comprehensive income (loss)	164,400,000	109,300,000	173,800,000	372,000,000
Other Subsidiaries
Revenues
Net earned premiums	217,100,000	227,500,000	405,600,000	478,900,000
Net investment income	105,700,000	106,300,000	206,900,000	207,200,000
Net realized investment gains (losses)	(3,100,000)	(5,100,000)	(1,800,000)	(2,300,000)
Net change in fair value of credit derivatives:
Realized Gains and Other Settlements	(22,200,000)	(10,800,000)	(79,100,000)	24,600,000
Unrealized Gains (Losses)	283,400,000	(54,000,000)	(350,400,000)	(325,600,000)
Net change in fair value of credit derivatives	261,200,000	(64,800,000)	(429,500,000)	(301,000,000)
Equity in earnings of subsidiaries	353,700,000	(53,000,000)	(6,300,000)	115,600,000
Other	181,900,000	(146,000,000)	222,700,000	16,100,000
Total revenues	1,116,500,000	64,900,000	397,600,000	514,500,000
Expenses
Loss and loss adjustment expenses	121,700,000	122,000,000	370,900,000	95,200,000
Amortization of deferred acquisition costs	9,100,000	9,700,000	18,000,000	20,800,000
Interest expense	6,500,000	5,200,000	11,600,000	10,500,000
Other operating expenses	49,100,000	47,800,000	104,200,000	102,900,000
Total expenses	186,400,000	184,700,000	504,700,000	229,400,000
Income (loss) before income taxes	930,100,000	(119,800,000)	(107,100,000)	285,100,000
Total provision (benefit) for income taxes	183,800,000	(40,900,000)	(24,600,000)	38,500,000
Net income (loss)	746,300,000	(78,900,000)	(82,500,000)	246,600,000
Comprehensive income (loss)	796,000,000	145,100,000	23,500,000	427,500,000
Consolidating Adjustments
Revenues
Net earned premiums	2,200,000	2,500,000	7,400,000	5,100,000
Net investment income	(4,400,000)	(3,800,000)	(8,100,000)	(7,500,000)
Net change in fair value of credit derivatives:
Realized Gains and Other Settlements	(500,000)		(500,000)
Net change in fair value of credit derivatives	(500,000)		(500,000)
Equity in earnings of subsidiaries	(1,264,200,000)	92,200,000	(67,900,000)	(690,800,000)
Other	(900,000)	(400,000)	(1,200,000)	(1,500,000)
Total revenues	(1,267,800,000)	90,500,000	(70,300,000)	(694,700,000)
Expenses
Loss and loss adjustment expenses	800,000	1,900,000	(1,600,000)	3,200,000
Amortization of deferred acquisition costs	(4,600,000)	(3,900,000)	(8,100,000)	(11,300,000)
Interest expense	(4,400,000)	(3,800,000)	(8,100,000)	(7,500,000)
Other operating expenses	(1,600,000)	(300,000)	(2,500,000)	(1,700,000)
Total expenses	(9,800,000)	(6,100,000)	(20,300,000)	(17,300,000)
Income (loss) before income taxes	(1,258,000,000)	96,600,000	(50,000,000)	(677,400,000)
Total provision (benefit) for income taxes	(5,900,000)	900,000	5,700,000	3,700,000
Net income (loss)	(1,252,100,000)	95,700,000	(55,700,000)	(681,100,000)
Comprehensive income (loss)	$ (1,333,300,000)	$ (306,500,000)	$ (235,300,000)	$ (1,002,400,000)