Subsidiary Information - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Assets
Total investment portfolio and cash	$ 10,905	$ 11,358
Investment in subsidiaries	0	0
Premiums receivable, net of commissions payable	623	693
Ceded unearned premium reserve	228	232
Deferred acquisition costs	110	114
Reinsurance recoverable on unpaid losses	82	69
Credit derivative assets	36	81
Deferred tax asset, net	235	276
Intercompany receivable	0	0
Financial guaranty variable interest entities’ assets, at fair value	814	1,261
Funds restricted for CIFG acquisition	451	0
Other	608	460
Total assets	14,092	14,544
Liabilities and shareholders’ equity
Unearned premium reserve	3,617	3,996
Loss and loss adjustment expense reserve	1,268	1,067
Long-term debt	1,303	1,300
Intercompany payable	0	0
Credit derivative liabilities	432	446
Deferred tax liabilities, net	0	0
Financial guaranty variable interest entities’ liabilities, at fair value	905	1,349
Other	317	323
Total liabilities	7,842	8,481
Effect on shareholders' equity (decrease) increase	6,250	6,063
Noncontrolling interest	0	0
Total shareholders' equity	6,250	6,063
Total liabilities and shareholders’ equity	14,092	14,544
Reportable Legal Entities [Member] | Assured Guaranty Ltd. (Parent) [Member]
Assets
Total investment portfolio and cash	42	10
Investment in subsidiaries	6,173	5,961
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
Funds restricted for CIFG acquisition	0
Other	39	98
Total assets	6,254	6,069
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	4	6
Total liabilities	4	6
Effect on shareholders' equity (decrease) increase	6,250	6,063
Noncontrolling interest	0	0
Total shareholders' equity	6,250	6,063
Total liabilities and shareholders’ equity	6,254	6,069
Reportable Legal Entities [Member] | AGUS (Issuer) [Member]
Assets
Total investment portfolio and cash	85	156
Investment in subsidiaries	5,705	5,569
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	29	52
Intercompany receivable	0	0
Financial guaranty variable interest entities’ assets, at fair value	0	0
Funds restricted for CIFG acquisition	0
Other	63	29
Total assets	5,882	5,806
Liabilities and shareholders’ equity
Unearned premium reserve	0	0
Loss and loss adjustment expense reserve	0	0
Long-term debt	842	842
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	15	82
Total liabilities	947	1,014
Effect on shareholders' equity (decrease) increase	4,935	4,792
Noncontrolling interest	0	0
Total shareholders' equity	4,935	4,792
Total liabilities and shareholders’ equity	5,882	5,806
Reportable Legal Entities [Member] | AGMH (Issuer) [Member]
Assets
Total investment portfolio and cash	20	22
Investment in subsidiaries	4,167	4,081
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
Funds restricted for CIFG acquisition	0
Other	35	26
Total assets	4,222	4,129
Liabilities and shareholders’ equity
Unearned premium reserve	0	0
Loss and loss adjustment expense reserve	0	0
Long-term debt	449	445
Intercompany payable	0	0
Credit derivative liabilities	0	0
Deferred tax liabilities, net	90	91
Financial guaranty variable interest entities’ liabilities, at fair value	0	0
Other	14	15
Total liabilities	553	551
Effect on shareholders' equity (decrease) increase	3,669	3,578
Noncontrolling interest	0	0
Total shareholders' equity	3,669	3,578
Total liabilities and shareholders’ equity	4,222	4,129
Reportable Legal Entities [Member] | Other Entities [Member]
Assets
Total investment portfolio and cash	11,113	11,530
Investment in subsidiaries	284	377
Premiums receivable, net of commissions payable	748	833
Ceded unearned premium reserve	1,189	1,266
Deferred acquisition costs	167	176
Reinsurance recoverable on unpaid losses	532	467
Credit derivative assets	144	207
Deferred tax asset, net	335	357
Intercompany receivable	90	90
Financial guaranty variable interest entities’ assets, at fair value	814	1,261
Funds restricted for CIFG acquisition	451
Other	756	571
Total assets	16,623	17,135
Liabilities and shareholders’ equity
Unearned premium reserve	4,675	5,143
Loss and loss adjustment expense reserve	1,790	1,537
Long-term debt	12	13
Intercompany payable	300	300
Credit derivative liabilities	540	572
Deferred tax liabilities, net	0	0
Financial guaranty variable interest entities’ liabilities, at fair value	905	1,349
Other	692	622
Total liabilities	8,914	9,536
Effect on shareholders' equity (decrease) increase	7,425	7,222
Noncontrolling interest	284	377
Total shareholders' equity	7,709	7,599
Total liabilities and shareholders’ equity	16,623	17,135
Consolidating Adjustments [Member]
Assets
Total investment portfolio and cash	(355)	(360)
Investment in subsidiaries	(16,329)	(15,988)
Premiums receivable, net of commissions payable	(125)	(140)
Ceded unearned premium reserve	(961)	(1,034)
Deferred acquisition costs	(57)	(62)
Reinsurance recoverable on unpaid losses	(450)	(398)
Credit derivative assets	(108)	(126)
Deferred tax asset, net	(129)	(133)
Intercompany receivable	(90)	(90)
Financial guaranty variable interest entities’ assets, at fair value	0	0
Funds restricted for CIFG acquisition	0
Other	(285)	(264)
Total assets	(18,889)	(18,595)
Liabilities and shareholders’ equity
Unearned premium reserve	(1,058)	(1,147)
Loss and loss adjustment expense reserve	(522)	(470)
Long-term debt	0	0
Intercompany payable	(390)	(390)
Credit derivative liabilities	(108)	(126)
Deferred tax liabilities, net	(90)	(91)
Financial guaranty variable interest entities’ liabilities, at fair value	0	0
Other	(408)	(402)
Total liabilities	(2,576)	(2,626)
Effect on shareholders' equity (decrease) increase	(16,029)	(15,592)
Noncontrolling interest	(284)	(377)
Total shareholders' equity	(16,313)	(15,969)
Total liabilities and shareholders’ equity	$ (18,889)	$ (18,595)