Condensed Consolidated Statement of Shareholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Common Shares	Retained Earnings	Accumulated Other Comprehensive Income	Deferred Equity Compensation	Total Shareholders’ Equity Attributable to Assured Guaranty Ltd.	Nonredeemable Noncontrolling Interests
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	220		214			214	6
Dividends	(53)		(53)			(53)
Reallocation of ownership interest	10						10
Contributions	44						44
Common share repurchases (in shares)		(11,443,155)
Common shares repurchases	(320)		(320)			(320)
Shared based compensation (in shares)		417,453
Share-based compensation	7		7			7
Distributions	(19)						(19)
Other comprehensive income (loss)	62			62		62
Ending balance (in shares) at Sep. 30, 2020		82,249,285
Ending balance at Sep. 30, 2020	6,596	$ 1	6,143	404	1	6,549	47
Beginning balance (in shares) at Jun. 30, 2020		84,062,384
Beginning balance at Jun. 30, 2020	6,489	$ 1	6,109	333	1	6,444	45
Increase (Decrease) in Shareholders' Equity
Net income	88		86			86	2
Dividends	(17)		(17)			(17)
Contributions	3						3
Common share repurchases (in shares)		(1,857,323)
Common shares repurchases	(40)		(40)			(40)
Shared based compensation (in shares)		44,224
Share-based compensation	5		5			5
Distributions	(3)						(3)
Other comprehensive income (loss)	71			71		71
Ending balance (in shares) at Sep. 30, 2020		82,249,285
Ending balance at Sep. 30, 2020	6,596	$ 1	6,143	404	1	6,549	47
Beginning balance (in shares) at Dec. 31, 2020		77,546,896
Beginning balance at Dec. 31, 2020	6,684	$ 1	6,143	498	1	6,643	41
Increase (Decrease) in Shareholders' Equity
Net income	137		126			126	11
Dividends	(50)		(50)			(50)
Contributions	34						34
Common share repurchases (in shares)		(6,793,058)
Common shares repurchases	(305)		(305)			(305)
Shared based compensation (in shares)		488,102
Share-based compensation	10		10			10
Distributions	(11)						(11)
Other comprehensive income (loss)	(124)			(124)		(124)
Ending balance (in shares) at Sep. 30, 2021		71,241,940
Ending balance at Sep. 30, 2021	6,375	$ 1	5,924	374	1	6,300	75
Beginning balance (in shares) at Jun. 30, 2021		74,112,554
Beginning balance at Jun. 30, 2021	6,552	$ 1	6,056	445	1	6,503	49
Increase (Decrease) in Shareholders' Equity
Net income	20		17			17	3
Dividends	(16)		(16)			(16)
Contributions	25						25
Common share repurchases (in shares)		(2,918,993)
Common shares repurchases	(140)		(140)			(140)
Shared based compensation (in shares)		48,379
Share-based compensation	7		7			7
Distributions	(2)						(2)
Other comprehensive income (loss)	(71)			(71)		(71)
Ending balance (in shares) at Sep. 30, 2021		71,241,940
Ending balance at Sep. 30, 2021	$ 6,375	$ 1	$ 5,924	$ 374	$ 1	$ 6,300	$ 75