Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income (loss)	$ 775,620	$ 493,707	$ 84,822
Unrealized holding gains (losses) arising during the period, net of tax provision (benefit) of $110,277, $(42,585), and $66,835	242,657	(27,720)	165,929
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(7,358), $(2,829), and $1,435	(14,290)	1,543	(34,097)
Change in net unrealized gains on investments	256,947	(29,263)	200,026
Change in cumulative translation adjustment, net of tax provision (benefit) of $(407), $(229) and $(759)	(779)	(384)	(3,000)
Change in cash flow hedge, net of tax provision (benefit) of $(225), $(225) and $(225)	(418)	(418)	(418)
Other comprehensive income (loss)	255,750	(30,065)	196,608
Comprehensive income (loss)	1,031,370	463,642	281,430
Less: Comprehensive income (loss) attributable to noncontrolling interest of variable interest entities			(1,127)
Comprehensive income (loss) of Assured Guaranty Ltd.	$ 1,031,370	$ 463,642	$ 282,557