Subsidiary Information - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets
Total investment portfolio and cash	$ 11,358		$ 11,459
Investment in subsidiaries	0		0
Premiums receivable, net of commissions payable	693		729
Ceded unearned premium reserve	232		381
Deferred acquisition costs	114		121	$ 124	$ 116
Reinsurance recoverable on unpaid losses	69		78
Credit derivative assets	81		68
Deferred tax asset, net	276		260
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	1,261	[1]	1,402
Other	460		421
Total assets	14,544		14,919
Liabilities and shareholders’ equity
Unearned premium reserve	3,996		4,261
Loss and loss adjustment expense reserve	1,067		799
Long-term debt	1,300		1,297
Intercompany payable	0		0
Credit derivative liabilities	446		963
Deferred tax liabilities, net	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	1,349	[1]	1,419
Other	323		422
Total liabilities	8,481		9,161
Effect on shareholders’ equity (decrease) increase	6,063		5,758	$ 5,115	$ 4,994
Noncontrolling interest	0		0
Total shareholders' equity	6,063		5,758
Total liabilities and shareholders’ equity	14,544		14,919
Reportable Legal Entities [Member] | Assured Guaranty Ltd. (Parent) [Member]
Assets
Total investment portfolio and cash	10		126
Investment in subsidiaries	5,961		5,612
Premiums receivable, net of commissions payable	0		0
Ceded unearned premium reserve	0		0
Deferred acquisition costs	0		0
Reinsurance recoverable on unpaid losses	0		0
Credit derivative assets	0		0
Deferred tax asset, net	0		0
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	98		27
Total assets	6,069		5,765
Liabilities and shareholders’ equity
Unearned premium reserve	0		0
Loss and loss adjustment expense reserve	0		0
Long-term debt	0		0
Intercompany payable	0		0
Credit derivative liabilities	0		0
Deferred tax liabilities, net	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	6		7
Total liabilities	6		7
Effect on shareholders’ equity (decrease) increase	6,063		5,758
Noncontrolling interest	0		0
Total shareholders' equity	6,063		5,758
Total liabilities and shareholders’ equity	6,069		5,765
Reportable Legal Entities [Member] | AGUS (Issuer) [Member]
Assets
Total investment portfolio and cash	156		204
Investment in subsidiaries	5,569		5,072
Premiums receivable, net of commissions payable	0		0
Ceded unearned premium reserve	0		0
Deferred acquisition costs	0		0
Reinsurance recoverable on unpaid losses	0		0
Credit derivative assets	0		0
Deferred tax asset, net	52		54
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	29		71
Total assets	5,806		5,401
Liabilities and shareholders’ equity
Unearned premium reserve	0		0
Loss and loss adjustment expense reserve	0		0
Long-term debt	842		841
Intercompany payable	90		90
Credit derivative liabilities	0		0
Deferred tax liabilities, net	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	82		9
Total liabilities	1,014		940
Effect on shareholders’ equity (decrease) increase	4,792		4,461
Noncontrolling interest	0		0
Total shareholders' equity	4,792		4,461
Total liabilities and shareholders’ equity	5,806		5,401
Reportable Legal Entities [Member] | AGMH (Issuer) [Member]
Assets
Total investment portfolio and cash	22		47
Investment in subsidiaries	4,081		3,965
Premiums receivable, net of commissions payable	0		0
Ceded unearned premium reserve	0		0
Deferred acquisition costs	0		0
Reinsurance recoverable on unpaid losses	0		0
Credit derivative assets	0		0
Deferred tax asset, net	0		0
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	26		27
Total assets	4,129		4,039
Liabilities and shareholders’ equity
Unearned premium reserve	0		0
Loss and loss adjustment expense reserve	0		0
Long-term debt	445		437
Intercompany payable	0		0
Credit derivative liabilities	0		0
Deferred tax liabilities, net	91		94
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	15		16
Total liabilities	551		547
Effect on shareholders’ equity (decrease) increase	3,578		3,492
Noncontrolling interest	0		0
Total shareholders' equity	3,578		3,492
Total liabilities and shareholders’ equity	4,129		4,039
Reportable Legal Entities [Member] | Other Entities [Member]
Assets
Total investment portfolio and cash	11,530		11,382
Investment in subsidiaries	377		339
Premiums receivable, net of commissions payable	833		864
Ceded unearned premium reserve	1,266		1,469
Deferred acquisition costs	176		186
Reinsurance recoverable on unpaid losses	467		338
Credit derivative assets	207		277
Deferred tax asset, net	357		295
Intercompany receivable	90		90
Financial guaranty variable interest entities’ assets, at fair value	1,261		1,402
Other	571		538
Total assets	17,135		17,180
Liabilities and shareholders’ equity
Unearned premium reserve	5,143		5,328
Loss and loss adjustment expense reserve	1,537		1,066
Long-term debt	13		19
Intercompany payable	300		300
Credit derivative liabilities	572		1,172
Deferred tax liabilities, net	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	1,349		1,419
Other	622		764
Total liabilities	9,536		10,068
Effect on shareholders’ equity (decrease) increase	7,222		6,773
Noncontrolling interest	377		339
Total shareholders' equity	7,599		7,112
Total liabilities and shareholders’ equity	17,135		17,180
Consolidating Adjustments [Member]
Assets
Total investment portfolio and cash	(360)		(300)
Investment in subsidiaries	(15,988)		(14,988)
Premiums receivable, net of commissions payable	(140)		(135)
Ceded unearned premium reserve	(1,034)		(1,088)
Deferred acquisition costs	(62)		(65)
Reinsurance recoverable on unpaid losses	(398)		(260)
Credit derivative assets	(126)		(209)
Deferred tax asset, net	(133)		(89)
Intercompany receivable	(90)		(90)
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	(264)		(242)
Total assets	(18,595)		(17,466)
Liabilities and shareholders’ equity
Unearned premium reserve	(1,147)		(1,067)
Loss and loss adjustment expense reserve	(470)		(267)
Long-term debt	0		0
Intercompany payable	(390)		(390)
Credit derivative liabilities	(126)		(209)
Deferred tax liabilities, net	(91)		(94)
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	(402)		(374)
Total liabilities	(2,626)		(2,401)
Effect on shareholders’ equity (decrease) increase	(15,592)		(14,726)
Noncontrolling interest	(377)		(339)
Total shareholders' equity	(15,969)		(15,065)
Total liabilities and shareholders’ equity	$ (18,595)		$ (17,466)

[1] The December 31, 2015 amounts include $111 million of FG VIE assets and $107 million of FG VIE liabilities acquired from Radian Asset.