Subsidiary Information (Details 2) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Revenues
Net earned premiums	$ 193,677,000	$ 253,977,000
Net investment income	97,762,000	97,412,000
Net realized investment gains (losses)	1,316,000	2,806,000
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	(56,881,000)	35,427,000
Net unrealized gains (losses)	(633,758,000)	(271,636,000)
Net change in fair value of credit derivatives	(690,639,000)	(236,209,000)
Other	40,500,000	161,000,000
Total revenues	(357,406,000)	278,913,000
Expenses
Loss and LAE	246,847,000	(25,580,000)
Amortization of deferred acquisition costs	5,413,000	3,662,000	0
Interest expense	24,673,000	24,760,000
Other operating expenses	61,280,000	62,883,000
Total expenses	338,213,000	65,725,000	0
Income (loss) before income taxes	(695,619,000)	213,188,000
Total provision (benefit) for income taxes	(212,595,000)	73,932,000
Net income (loss)	(483,024,000)	139,256,000	0
Other comprehensive income (loss)	30,888,000	(25,436,000)
Assured Guaranty Ltd. (Parent)
Net change in fair value of credit derivatives:
Equity in earnings of subsidiaries	(476,500,000)	147,700,000
Total revenues	(476,500,000)	147,700,000
Expenses
Other operating expenses	6,500,000	8,400,000
Total expenses	6,500,000	8,400,000
Income (loss) before income taxes	(483,000,000)	139,300,000
Net income (loss)	(483,000,000)	139,300,000
Other comprehensive income (loss)	30,900,000	(25,400,000)
AGUS (Issuer)
Net change in fair value of credit derivatives:
Equity in earnings of subsidiaries	(353,300,000)	175,100,000
Total revenues	(353,300,000)	175,100,000
Expenses
Interest expense	9,900,000	9,800,000
Other operating expenses	400,000	200,000
Total expenses	10,300,000	10,000,000
Income (loss) before income taxes	(363,600,000)	165,100,000
Total provision (benefit) for income taxes	(3,600,000)	(3,500,000)
Net income (loss)	(360,000,000)	168,600,000
Other comprehensive income (loss)	25,100,000	(17,800,000)
AGMH (Issuer)
Revenues
Net investment income	300,000	200,000
Net change in fair value of credit derivatives:
Equity in earnings of subsidiaries	(6,500,000)	291,600,000
Total revenues	(6,200,000)	291,800,000
Expenses
Interest expense	13,400,000	13,400,000
Other operating expenses	200,000	500,000
Total expenses	13,600,000	13,900,000
Income (loss) before income taxes	(19,800,000)	277,900,000
Total provision (benefit) for income taxes	(12,200,000)	(4,800,000)
Net income (loss)	(7,600,000)	282,700,000
Other comprehensive income (loss)	17,000,000	(20,000,000)
Other Subsidiaries
Revenues
Net earned premiums	188,500,000	251,400,000
Net investment income	101,200,000	100,900,000
Net realized investment gains (losses)	1,300,000	2,800,000
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	(56,900,000)	35,400,000
Net unrealized gains (losses)	(633,800,000)	(271,600,000)
Net change in fair value of credit derivatives	(690,700,000)	(236,200,000)
Equity in earnings of subsidiaries	(360,000,000)	168,600,000
Other	40,800,000	162,100,000
Total revenues	(718,900,000)	449,600,000
Expenses
Loss and LAE	249,200,000	(26,800,000)
Amortization of deferred acquisition costs	8,900,000	11,100,000
Interest expense	5,100,000	5,300,000
Other operating expenses	55,100,000	55,100,000
Total expenses	318,300,000	44,700,000
Income (loss) before income taxes	(1,037,200,000)	404,900,000
Total provision (benefit) for income taxes	(208,400,000)	79,400,000
Net income (loss)	(828,800,000)	325,500,000
Other comprehensive income (loss)	56,300,000	(43,100,000)
Consolidating Adjustments
Revenues
Net earned premiums	5,200,000	2,600,000
Net investment income	(3,700,000)	(3,700,000)
Net change in fair value of credit derivatives:
Equity in earnings of subsidiaries	1,196,300,000	(783,000,000)
Other	(300,000)	(1,100,000)
Total revenues	1,197,500,000	(785,200,000)
Expenses
Loss and LAE	(2,400,000)	1,300,000
Amortization of deferred acquisition costs	(3,500,000)	(7,400,000)
Interest expense	(3,700,000)	(3,700,000)
Other operating expenses	(900,000)	(1,400,000)
Total expenses	(10,500,000)	(11,200,000)
Income (loss) before income taxes	1,208,000,000	(774,000,000)
Total provision (benefit) for income taxes	11,600,000	2,800,000
Net income (loss)	1,196,400,000	(776,800,000)
Other comprehensive income (loss)	$ (98,400,000)	$ 80,900,000