Parent Company - Condensed Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Cash Flow Statements, Captions [Line Items]
Net income	$ 389	$ 362	$ 402
Equity in earnings of investees	(94)	(27)	(4)
Net cash flows provided by (used in) operating activities	(1,937)	(853)	(509)
Purchases	0	(85)	(229)
Maturities and paydowns	1,148	878	781
Net cash flows provided by (used in) investing activities	23	788	1,169
Dividends paid	(66)	(69)	(74)
Repurchases of common shares	(496)	(446)	(500)
Other	26	(10)	(15)
Net cash flows provided by (used in) financing activities	1,960	183	(584)
Increase (decrease) in cash and cash equivalents and restricted cash	44	115	79
Cash and cash equivalents and restricted cash at beginning of period	298	183	104
Cash and cash equivalents and restricted cash at end of period	342	298	183
AG Re | Assured Guaranty LTD | Fixed-maturity securities
Condensed Cash Flow Statements, Captions [Line Items]
Dividend from a subsidiary in the form of fixed-maturity securities	46	47	0
Assured Guaranty Ltd. (Parent)
Condensed Cash Flow Statements, Captions [Line Items]
Net income	389	362	402
Equity in earnings of investees	(423)	(396)	(433)
Cash dividends from subsidiaries	539	547	689
Other	22	19	21
Net cash flows provided by (used in) operating activities	527	532	679
Purchases	0	(4)	0
Maturities and paydowns	4	0	0
Net sales (purchases) of short-term investments with original maturities of less than three months	41	(3)	(90)
Net cash flows provided by (used in) investing activities	45	(7)	(90)
Dividends paid	(66)	(69)	(74)
Repurchases of common shares	(496)	(446)	(500)
Other	(10)	(10)	(15)
Net cash flows provided by (used in) financing activities	(572)	(525)	(589)
Increase (decrease) in cash and cash equivalents and restricted cash	0	0	0
Cash and cash equivalents and restricted cash at beginning of period	0	0	0
Cash and cash equivalents and restricted cash at end of period	$ 0	$ 0	$ 0