Condensed Consolidated Statement of Shareholders' Equity (unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Deferred Equity Compensation [Member]	Total Shareholders' Equity Attributable to Assured Guaranty Ltd. [Member]	Noncontrolling Interest [Member]
Beginning balance (in shares) at Dec. 31, 2018		103,672,592
Beginning balance at Dec. 31, 2018	$ 6,555	$ 1	$ 86	$ 6,374	$ 93	$ 1	$ 6,555	$ 0
Increase (Decrease) in Shareholders' Equity
Net Income (Loss)	196			196			196
Dividends	(38)			(38)			(38)
Common stock repurchases (in shares)		(4,427,735)
Common stock repurchases	(190)		(83)	(107)			(190)
Shared based compensation (in shares)		556,155
Share based compensation	(3)		(3)				(3)
Other comprehensive income	202				202		202
Ending balance (in shares) at Jun. 30, 2019		99,801,012
Ending balance at Jun. 30, 2019	6,722	$ 1	0	6,425	295	1	6,722	0
Beginning balance (in shares) at Mar. 31, 2019		102,270,409
Beginning balance at Mar. 31, 2019	6,669	$ 1	0	6,406	261	1	6,669	0
Increase (Decrease) in Shareholders' Equity
Net Income (Loss)	142			142			142
Dividends	(19)			(19)			(19)
Common stock repurchases (in shares)		(2,519,130)
Common stock repurchases	(111)		(7)	(104)			(111)
Shared based compensation (in shares)		49,733
Share based compensation	7		7				7
Other comprehensive income	34				34		34
Ending balance (in shares) at Jun. 30, 2019		99,801,012
Ending balance at Jun. 30, 2019	6,722	$ 1	$ 0	6,425	295	1	6,722	0
Beginning balance (in shares) at Dec. 31, 2019		93,274,987
Beginning balance at Dec. 31, 2019	6,645	$ 1		6,295	342	1	6,639	6
Increase (Decrease) in Shareholders' Equity
Net Income (Loss)	132			128			128	4
Dividends	(36)			(36)			(36)
Reallocation of ownership interests	10							10
Contributions	41							41
Common stock repurchases (in shares)		(9,585,832)
Common stock repurchases	(280)			(280)			(280)
Shared based compensation (in shares)		373,229
Share based compensation	2			2			2
Distributions	(16)							(16)
Other comprehensive income	(9)				(9)		(9)
Ending balance (in shares) at Jun. 30, 2020		84,062,384
Ending balance at Jun. 30, 2020	6,489	$ 1		6,109	333	1	6,444	45
Beginning balance (in shares) at Mar. 31, 2020		89,983,322
Beginning balance at Mar. 31, 2020	6,265	$ 1		6,100	138	1	6,240	25
Increase (Decrease) in Shareholders' Equity
Net Income (Loss)	188			183			183	5
Dividends	(17)			(17)			(17)
Reallocation of ownership interests	8							8
Contributions	23							23
Common stock repurchases (in shares)		(5,956,422)
Common stock repurchases	(164)			(164)			(164)
Shared based compensation (in shares)		35,484
Share based compensation	7			7			7
Distributions	(16)							(16)
Other comprehensive income	195				195		195
Ending balance (in shares) at Jun. 30, 2020		84,062,384
Ending balance at Jun. 30, 2020	$ 6,489	$ 1		$ 6,109	$ 333	$ 1	$ 6,444	$ 45