Expected Loss to be Paid (Recovered) - Net Expected Loss to be Paid (Recovered) and Net Economic Loss Development (Benefit) by Accounting Model (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Schedule of Expected Losses to be Paid [Line Items]
Net Expected Loss to be Paid (Recovered)	$ 104	$ 306	$ 104	$ 306	$ 186	$ 106	$ 447	$ 505
Net economic loss development (benefit)	(38)	(34)	(17)	(20)
Insurance
Schedule of Expected Losses to be Paid [Line Items]
Net Expected Loss to be Paid (Recovered)	92		92			90
Net economic loss development (benefit)	(35)	(31)	51	(19)
FG VIEs' assets
Schedule of Expected Losses to be Paid [Line Items]
Net Expected Loss to be Paid (Recovered)	12		12			16
Net economic loss development (benefit)	(4)	(1)	(5)	0
Credit derivatives
Schedule of Expected Losses to be Paid [Line Items]
Net Expected Loss to be Paid (Recovered)	0		0			$ 0
Net economic loss development (benefit)	$ 1	$ (2)	$ (63)	$ (1)

ASSURED GUARANTY LTD 10-Q