Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues
Net earned premiums	$ 920,055	$ 1,186,705	$ 930,429
Net investment income	391,017	354,703	259,222
Net realized investment gains (losses):
Other-than-temporary impairment losses	(83,792)	(44,672)	(74,022)
Less: portion of other-than-temporary impairment loss recognized in other comprehensive income	(39,150)	(17,292)	(28,176)
Other net realized investment gains (losses)	26,650	25,386	13,184
Net realized investment gains (losses)	(17,992)	(1,994)	(32,662)
Net change in fair value of credit derivatives:
Realized gains and other settlements	5,959	153,495	163,558
Net unrealized gains (losses)	553,779	(155,106)	(337,810)
Net change in fair value of credit derivatives	559,738	(1,611)	(174,252)
Fair value gain (loss) on committed capital securities	35,130	9,195	(122,940)
Net change in fair value of financial guaranty variable interest entities	(131,984)	(273,652)	(1,156)
Other income	63,349	40,107	58,518
Total Revenues	1,819,313	1,313,453	917,159
Expenses
Loss and loss adjustment expenses	461,890	412,161	393,800
Amortization of deferred acquisition costs	30,849	34,057	53,899
Assured Guaranty Municipal Holdings Inc. acquisition-related expenses		6,772	92,239
Interest expense	99,112	99,621	62,783
Goodwill and settlement of pre-existing relationship			23,341
Other operating expenses	193,000	211,536	174,165
Total expenses	784,851	764,147	800,227
Income (loss) before income taxes	1,034,462	549,306	116,932
Provision (benefit) for income taxes
Current	(126,904)	(25,151)	217,253
Deferred	385,746	80,750	(185,143)
Total provision (benefit) for income taxes	258,842	55,599	32,110
Net income (loss)	775,620	493,707	84,822
Less: Noncontrolling interest of variable interest entities			(1,156)
Net income (loss) attributable to Assured Guaranty Ltd.	$ 775,620	$ 493,707	$ 85,978
Earnings per share:
Basic (in dollars per share)	$ 4.23	$ 2.68	$ 0.68
Diluted (in dollars per share)	$ 4.18	$ 2.61	$ 0.66
Dividends per share (in dollars per share)	$ 0.18	$ 0.18	$ 0.18