Parent Company - Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Condensed Balance Sheet Statements, Captions [Line Items]
Other assets	$ 746	$ 706
Total assets	11,901	12,539
Other liabilities (includes $34000000 and $53000000 at fair value)	498	492
Total liabilities	6,348	6,774
Total shareholders’ equity attributable to AGL	5,495	5,713
Total liabilities and shareholders’ equity	11,901	12,539
Assured Guaranty Ltd. (Parent)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	66	40
Investments in subsidiaries	5,237	5,553
Dividends receivable from subsidiaries	150	80
Other assets	69	64
Total assets	5,522	5,737
Other liabilities (includes $34000000 and $53000000 at fair value)	27	24
Total liabilities	27	24
Total shareholders’ equity attributable to AGL	5,495	5,713
Total liabilities and shareholders’ equity	$ 5,522	$ 5,737