Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 188	$ 142	$ 130	$ 196
Change in net unrealized gains (losses) on:
Investments with no credit impairment recognized in the statement of operations, net of tax provision (benefit) of $31, $19, $4 and $44	175	79	13	242
Investments with credit impairment recognized in the statement of operations, net of tax provision (benefit) of $6, $(12), $(7) and $(12)	25	(48)	(27)	(43)
Change in net unrealized gains (losses) on investments	200	31	(14)	199
Change in net unrealized gains (losses) on financial guaranty variable interest entities' liabilities with recourse, net of tax	(5)	4	5	4
Other, net of tax provision (benefit)	0	(1)	0	(1)
Other comprehensive income (loss)	195	34	(9)	202
Comprehensive income (loss)	383	176	121	398
Less: Comprehensive income (loss) attributable to noncontrolling interest	5	0	2	0
Comprehensive income (loss) attributable to Assured Guaranty Ltd.	$ 378	$ 176	$ 119	$ 398