Subsidiary Information - Condensed Consolidating Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013	Mar. 31, 2013		Dec. 31, 2012
Assets
Total investment portfolio and cash	$ 11,167		$ 10,969
Investment in subsidiaries	0		0
Premiums receivable, net of commissions payable	863	[1]	876	956	[1]	1,005
Ceded unearned premium reserve	454		452
Deferred acquisition costs	122		124
Reinsurance recoverable on unpaid losses	37		36
Credit derivative assets	78		94
Deferred tax asset, net	637		688
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	1,257		2,565
Other	491		483
Total assets	15,106		16,287
Liabilities and shareholders’ equity
Unearned premium reserve	4,504		4,595
Loss and loss adjustment expense reserve	636		592
Long-term debt	812		816
Intercompany payable	0		0
Credit derivative liabilities	2,001		1,787
Deferred Tax Liabilities, Net	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	1,447		2,871
Other	497		511
Total liabilities	9,897		11,172
TOTAL SHAREHOLDERS’ EQUITY ATTRIBUTABLE TO ASSURED GUARANTY LTD.	5,209		5,115
Noncontrolling interest	0		0
TOTAL SHAREHOLDERS' EQUITY	5,209		5,115
Total liabilities and shareholders’ equity	15,106		16,287
Assured Guaranty Ltd. (Parent)
Assets
Total investment portfolio and cash	36		33
Investment in subsidiaries	5,158		5,066
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	20		23
Total assets	5,214		5,122
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	5		7
Total liabilities	5		7
TOTAL SHAREHOLDERS’ EQUITY ATTRIBUTABLE TO ASSURED GUARANTY LTD.	5,209		5,115
Noncontrolling interest	0		0
TOTAL SHAREHOLDERS' EQUITY	5,209		5,115
Total liabilities and shareholders’ equity	5,214		5,122
AGUS (Issuer)
Assets
Total investment portfolio and cash	186		186
Investment in subsidiaries	4,360		4,191
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	108		97
Intercompany receivable	0		0
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	9		17
Total assets	4,663		4,491
Liabilities and shareholders’ equity
Unearned premium reserve	0		0
Loss and loss adjustment expense reserve	0		0
Long-term debt	348		348
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	14		7
Total liabilities	452		445
TOTAL SHAREHOLDERS’ EQUITY ATTRIBUTABLE TO ASSURED GUARANTY LTD.	4,211		4,046
Noncontrolling interest	0		0
TOTAL SHAREHOLDERS' EQUITY	4,211		4,046
Total liabilities and shareholders’ equity	4,663		4,491
AGMH (Issuer)
Assets
Total investment portfolio and cash	61		42
Investment in subsidiaries	3,769		3,574
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	35		31
Total assets	3,865		3,647
Liabilities and shareholders’ equity
Unearned premium reserve	0		0
Loss and loss adjustment expense reserve	0		0
Long-term debt	431		430
Intercompany payable	0		0
Credit derivative liabilities	0		0
Deferred Tax Liabilities, Net	95		95
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	21		16
Total liabilities	547		541
TOTAL SHAREHOLDERS’ EQUITY ATTRIBUTABLE TO ASSURED GUARANTY LTD.	3,318		3,106
Noncontrolling interest	0		0
TOTAL SHAREHOLDERS' EQUITY	3,318		3,106
Total liabilities and shareholders’ equity	3,865		3,647
Other Subsidiaries
Assets
Total investment portfolio and cash	11,184		11,008
Investment in subsidiaries	304		289
Premiums receivable, net of commissions payable	997		1,025
Ceded unearned premium reserve	1,582		1,598
Deferred acquisition costs	194		198
Reinsurance recoverable on unpaid losses	187		170
Credit derivative assets	510		482
Deferred tax asset, net	618		681
Intercompany receivable	90		90
Financial guaranty variable interest entities’ assets, at fair value	1,257		2,565
Other	603		638
Total assets	17,526		18,744
Liabilities and shareholders’ equity
Unearned premium reserve	5,611		5,720
Loss and loss adjustment expense reserve	791		733
Long-term debt	33		38
Intercompany payable	300		300
Credit derivative liabilities	2,433		2,175
Deferred Tax Liabilities, Net	0		0
Financial guaranty variable interest entities’ liabilities, at fair value	1,447		2,871
Other	762		853
Total liabilities	11,377		12,690
TOTAL SHAREHOLDERS’ EQUITY ATTRIBUTABLE TO ASSURED GUARANTY LTD.	5,845		5,765
Noncontrolling interest	304		289
TOTAL SHAREHOLDERS' EQUITY	6,149		6,054
Total liabilities and shareholders’ equity	17,526		18,744
Consolidating Adjustments
Assets
Total investment portfolio and cash	(300)		(300)
Investment in subsidiaries	(13,591)		(13,120)
Premiums receivable, net of commissions payable	(134)		(149)
Ceded unearned premium reserve	(1,128)		(1,146)
Deferred acquisition costs	(72)		(74)
Reinsurance recoverable on unpaid losses	(150)		(134)
Credit derivative assets	(432)		(388)
Deferred tax asset, net	(89)		(90)
Intercompany receivable	(90)		(90)
Financial guaranty variable interest entities’ assets, at fair value	0		0
Other	(176)		(226)
Total assets	(16,162)		(15,717)
Liabilities and shareholders’ equity
Unearned premium reserve	(1,107)		(1,125)
Loss and loss adjustment expense reserve	(155)		(141)
Long-term debt	0		0
Intercompany payable	(390)		(390)
Credit derivative liabilities	(432)		(388)
Deferred Tax Liabilities, Net	(95)		(95)
Financial guaranty variable interest entities’ liabilities, at fair value	0		0
Other	(305)		(372)
Total liabilities	(2,484)		(2,511)
TOTAL SHAREHOLDERS’ EQUITY ATTRIBUTABLE TO ASSURED GUARANTY LTD.	(13,374)		(12,917)
Noncontrolling interest	(304)		(289)
TOTAL SHAREHOLDERS' EQUITY	(13,678)		(13,206)
Total liabilities and shareholders’ equity	$ (16,162)		$ (15,717)

[1] Excludes $18 million and $28 million as of March 31, 2014 and March 31, 2013, respectively, related to consolidated FG VIEs.