Subsidiary Information - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Revenues
Net earned premiums	$ 236	$ 231	$ 214	$ 183	$ 192	$ 213	$ 219	$ 142	$ 864	[1]	$ 766	[1]	$ 570	[1]
Net investment income	117	94	98	99	112	112	98	101	408		423		403
Net realized investment gains (losses)	(24)	(2)	10	(13)	(6)	(27)	(9)	16	(29)		(26)		(60)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									29		(18)		23
Net unrealized gains (losses)									69		746		800
Net change in fair value of credit derivatives	74	21	63	(60)	428	86	90	124	98		728		823
Bargain purchase gain and settlement of pre-existing relationships	0	259	0	0	0	0	214	0	259		214		0
Other									77		102		258
Total revenues									1,677		2,207		1,994
Expenses
Loss and LAE	112	(9)	102	90	106	112	188	18	295		424		126
Amortization of DAC	5	4	5	4	5	5	6	4	18		20		25
Interest expense	25	26	25	26	25	25	26	25	102		101		92
Other operating expenses	57	65	63	60	55	54	66	56	245		231		220
Total expenses									660		776		463
Income (loss) before income taxes	271	480	201	65	584	172	409	266	1,017		1,431		1,531
Total (provision) benefit for income taxes	(74)	(1)	(55)	(6)	(155)	(43)	(112)	(65)	(136)		(375)		(443)
Equity in net earnings of subsidiaries									0		0		0
Net income (loss)									881		1,056		1,088
Less: noncontrolling interest									0		0		0
Net income (loss)	$ 197	$ 479	$ 146	$ 59	$ 429	$ 129	$ 297	$ 201	881		1,056		1,088
Comprehensive income (loss)									793		923		1,298
Reportable Legal Entities [Member] | Assured Guaranty Ltd. (Parent) [Member]
Revenues
Net earned premiums									0		0		0
Net investment income									0		0		0
Net realized investment gains (losses)									0		0		0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									0		0		0
Net unrealized gains (losses)									0		0		0
Net change in fair value of credit derivatives									0		0		0
Bargain purchase gain and settlement of pre-existing relationships									0		0
Other									0		0		0
Total revenues									0		0		0
Expenses
Loss and LAE									0		0		0
Amortization of DAC									0		0		0
Interest expense									0		0		0
Other operating expenses									29		30		31
Total expenses									29		30		31
Income (loss) before income taxes									(29)		(30)		(31)
Total (provision) benefit for income taxes									0		0		0
Equity in net earnings of subsidiaries									910		1,086		1,119
Net income (loss)									881		1,056		1,088
Less: noncontrolling interest									0		0		0
Net income (loss)									881		1,056		1,088
Comprehensive income (loss)									793		923		1,298
Reportable Legal Entities [Member] | AGUS (Issuer) [Member]
Revenues
Net earned premiums									0		0		0
Net investment income									0		1		0
Net realized investment gains (losses)									2		0		0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									0		0		0
Net unrealized gains (losses)									0		0		0
Net change in fair value of credit derivatives									0		0		0
Bargain purchase gain and settlement of pre-existing relationships									0		0
Other									0		0		0
Total revenues									2		1		0
Expenses
Loss and LAE									0		0		0
Amortization of DAC									0		0		0
Interest expense									52		52		40
Other operating expenses									2		1		1
Total expenses									54		53		41
Income (loss) before income taxes									(52)		(52)		(41)
Total (provision) benefit for income taxes									18		18		14
Equity in net earnings of subsidiaries									794		923		983
Net income (loss)									760		889		956
Less: noncontrolling interest									0		0		0
Net income (loss)									760		889		956
Comprehensive income (loss)									685		787		1,114
Reportable Legal Entities [Member] | AGMH (Issuer) [Member]
Revenues
Net earned premiums									0		0		0
Net investment income									0		0		1
Net realized investment gains (losses)									0		1		0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									0		0		0
Net unrealized gains (losses)									0		0		0
Net change in fair value of credit derivatives									0		0		0
Bargain purchase gain and settlement of pre-existing relationships									0		0
Other									0		0		0
Total revenues									0		1		1
Expenses
Loss and LAE									0		0		0
Amortization of DAC									0		0		0
Interest expense									54		54		54
Other operating expenses									2		1		1
Total expenses									56		55		55
Income (loss) before income taxes									(56)		(54)		(54)
Total (provision) benefit for income taxes									20		19		19
Equity in net earnings of subsidiaries									274		468		513
Net income (loss)									238		433		478
Less: noncontrolling interest									0		0		0
Net income (loss)									238		433		478
Comprehensive income (loss)									163		359		577
Reportable Legal Entities [Member] | Other Entities [Member]
Revenues
Net earned premiums									892		783		566
Net investment income									412		432		412
Net realized investment gains (losses)									(28)		(19)		(58)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									29		(18)		23
Net unrealized gains (losses)									69		773		800
Net change in fair value of credit derivatives									98		755		823
Bargain purchase gain and settlement of pre-existing relationships									257		54
Other									78		102		259
Total revenues									1,709		2,107		2,002
Expenses
Loss and LAE									296		434		122
Amortization of DAC									30		29		33
Interest expense									10		14		16
Other operating expenses									217		202		195
Total expenses									553		679		366
Income (loss) before income taxes									1,156		1,428		1,636
Total (provision) benefit for income taxes									(175)		(365)		(469)
Equity in net earnings of subsidiaries									44		39		32
Net income (loss)									1,025		1,102		1,199
Less: noncontrolling interest									44		39		32
Net income (loss)									981		1,063		1,167
Comprehensive income (loss)									953		967		1,570
Consolidating Adjustments [Member]
Revenues
Net earned premiums									(28)		(17)		4
Net investment income									(4)		(10)		(10)
Net realized investment gains (losses)									(3)		(8)		(2)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									0		0		0
Net unrealized gains (losses)									0		(27)		0
Net change in fair value of credit derivatives									0		(27)		0
Bargain purchase gain and settlement of pre-existing relationships									2		160
Other									(1)		0		(1)
Total revenues									(34)		98		(9)
Expenses
Loss and LAE									(1)		(10)		4
Amortization of DAC									(12)		(9)		(8)
Interest expense									(14)		(19)		(18)
Other operating expenses									(5)		(3)		(8)
Total expenses									(32)		(41)		(30)
Income (loss) before income taxes									(2)		139		21
Total (provision) benefit for income taxes									1		(47)		(7)
Equity in net earnings of subsidiaries									(2,022)		(2,516)		(2,647)
Net income (loss)									(2,023)		(2,424)		(2,633)
Less: noncontrolling interest									(44)		(39)		(32)
Net income (loss)									(1,979)		(2,385)		(2,601)
Comprehensive income (loss)									$ (1,801)		$ (2,113)		$ (3,261)

[1] Excludes $16 million, $21 million and $32 million for the year ended December 31, 2016, 2015 and 2014, respectively, related to consolidated FG VIEs.