Subsidiary Information - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues
Net earned premiums	$ 164	$ 183
Net investment income	122	99
Net realized investment gains (losses)	32	(13)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	15	8
Net unrealized gains (losses)	39	(68)
Net change in fair value of credit derivatives	54	(60)
Bargain purchase gain and settlement of pre-existing relationships	58	0
Other	97	36
Total revenues	527	245
Expenses
Loss and LAE	59	90
Amortization of deferred acquisition costs	4	4
Interest expense	24	26
Other operating expenses	68	60
Total expenses	155	180
Income (loss) before income taxes	372	65
Total (provision) benefit for income taxes	(55)	(6)
Equity in net earnings of subsidiaries	0	0
Net income (loss)	317	59
Less: noncontrolling interest	0	0
Net income (loss)	317	59
Comprehensive income (loss)	374	141
Reportable Legal Entities [Member] | Assured Guaranty Ltd. (Parent) [Member]
Revenues
Net earned premiums	0	0
Net investment income	0	0
Net realized investment gains (losses)	0	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0
Net unrealized gains (losses)	0	0
Net change in fair value of credit derivatives	0	0
Bargain purchase gain and settlement of pre-existing relationships	0
Other	3	0
Total revenues	3	0
Expenses
Loss and LAE	0	0
Amortization of deferred acquisition costs	0	0
Interest expense	0	0
Other operating expenses	10	8
Total expenses	10	8
Income (loss) before income taxes	(7)	(8)
Total (provision) benefit for income taxes	0	0
Equity in net earnings of subsidiaries	324	67
Net income (loss)	317	59
Less: noncontrolling interest	0	0
Net income (loss)	317	59
Comprehensive income (loss)	374	141
Reportable Legal Entities [Member] | AGUS (Issuer) [Member]
Revenues
Net earned premiums	0	0
Net investment income	0	0
Net realized investment gains (losses)	0	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0
Net unrealized gains (losses)	0	0
Net change in fair value of credit derivatives	0	0
Bargain purchase gain and settlement of pre-existing relationships	0
Other	0	0
Total revenues	0	0
Expenses
Loss and LAE	0	0
Amortization of deferred acquisition costs	0	0
Interest expense	12	13
Other operating expenses	6	0
Total expenses	18	13
Income (loss) before income taxes	(18)	(13)
Total (provision) benefit for income taxes	6	5
Equity in net earnings of subsidiaries	199	50
Net income (loss)	187	42
Less: noncontrolling interest	0	0
Net income (loss)	187	42
Comprehensive income (loss)	244	80
Reportable Legal Entities [Member] | AGMH (Issuer) [Member]
Revenues
Net earned premiums	0	0
Net investment income	0	0
Net realized investment gains (losses)	0	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0
Net unrealized gains (losses)	0	0
Net change in fair value of credit derivatives	0	0
Bargain purchase gain and settlement of pre-existing relationships	0
Other	0	0
Total revenues	0	0
Expenses
Loss and LAE	0	0
Amortization of deferred acquisition costs	0	0
Interest expense	13	13
Other operating expenses	1	1
Total expenses	14	14
Income (loss) before income taxes	(14)	(14)
Total (provision) benefit for income taxes	5	5
Equity in net earnings of subsidiaries	115	77
Net income (loss)	106	68
Less: noncontrolling interest	0	0
Net income (loss)	106	68
Comprehensive income (loss)	141	92
Reportable Legal Entities [Member] | Other Entities [Member]
Revenues
Net earned premiums	167	192
Net investment income	123	100
Net realized investment gains (losses)	32	(12)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	15	8
Net unrealized gains (losses)	39	(68)
Net change in fair value of credit derivatives	54	(60)
Bargain purchase gain and settlement of pre-existing relationships	58
Other	142	36
Total revenues	576	256
Expenses
Loss and LAE	11	93
Amortization of deferred acquisition costs	5	7
Interest expense	2	3
Other operating expenses	106	52
Total expenses	124	155
Income (loss) before income taxes	452	101
Total (provision) benefit for income taxes	(76)	(16)
Equity in net earnings of subsidiaries	8	9
Net income (loss)	384	94
Less: noncontrolling interest	8	9
Net income (loss)	376	85
Comprehensive income (loss)	437	178
Consolidating Adjustments [Member]
Revenues
Net earned premiums	(3)	(9)
Net investment income	(1)	(1)
Net realized investment gains (losses)	0	(1)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0
Net unrealized gains (losses)	0	0
Net change in fair value of credit derivatives	0	0
Bargain purchase gain and settlement of pre-existing relationships	0
Other	(48)	0
Total revenues	(52)	(11)
Expenses
Loss and LAE	48	(3)
Amortization of deferred acquisition costs	(1)	(3)
Interest expense	(3)	(3)
Other operating expenses	(55)	(1)
Total expenses	(11)	(10)
Income (loss) before income taxes	(41)	(1)
Total (provision) benefit for income taxes	10	0
Equity in net earnings of subsidiaries	(646)	(203)
Net income (loss)	(677)	(204)
Less: noncontrolling interest	(8)	(9)
Net income (loss)	(669)	(195)
Comprehensive income (loss)	$ (822)	$ (350)