Subsidiary Information - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues
Net earned premiums	[1]	$ 213	$ 144	$ 574	$ 412
Net investment income		112	102	311	301
Net realized investment gains (losses)		(27)	(19)	(20)	(25)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements		6	(14)	35	20
Net unrealized gains (losses)		80	269	265	127
Net change in fair value of credit derivatives	[2]	86	255	300	147
Bargain purchase gain and settlement of pre-existing relationships		0	0	214	0
Other		(16)	43	53	238
Total revenues		368	525	1,432	1,073
Expenses
Loss and LAE		112	(44)	318	54
Amortization of DAC		5	4	15	12
Interest expense		25	27	76	67
Other operating expenses		54	50	176	165
Total expenses		196	37	585	298
Income (loss) before income taxes		172	488	847	775
Total (provision) benefit for income taxes		(43)	(133)	(220)	(219)
Equity in net earnings of subsidiaries		0	0	0	0
Net income (loss)		129	355	627	556
Less: noncontrolling interest		0	0	0	0
Net income (loss)		129	355	627	556
Comprehensive income (loss)		163	356	530	729
Reportable Legal Entities [Member] | Assured Guaranty Ltd. (Parent) [Member]
Revenues
Net earned premiums		0	0	0	0
Net investment income		0	0	0	0
Net realized investment gains (losses)		0	0	0	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements		0	0	0	0
Net unrealized gains (losses)		0	0	0	0
Net change in fair value of credit derivatives		0	0	0	0
Bargain purchase gain and settlement of pre-existing relationships		0		0
Other		0	0	0	0
Total revenues		0	0	0	0
Expenses
Loss and LAE		0	0	0	0
Amortization of DAC		0	0	0	0
Interest expense		0	0	0	0
Other operating expenses		7	8	24	24
Total expenses		7	8	24	24
Income (loss) before income taxes		(7)	(8)	(24)	(24)
Total (provision) benefit for income taxes		0	0	0	0
Equity in net earnings of subsidiaries		136	363	651	580
Net income (loss)		129	355	627	556
Less: noncontrolling interest		0	0	0	0
Net income (loss)		129	355	627	556
Comprehensive income (loss)		163	356	530	729
Reportable Legal Entities [Member] | AGUS (Issuer) [Member]
Revenues
Net earned premiums		0	0	0	0
Net investment income		0	0	0	0
Net realized investment gains (losses)		0	0	0	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements		0	0	0	0
Net unrealized gains (losses)		0	0	0	0
Net change in fair value of credit derivatives		0	0	0	0
Bargain purchase gain and settlement of pre-existing relationships		0		0
Other		0	0	0	0
Total revenues		0	0	0	0
Expenses
Loss and LAE		0	0	0	0
Amortization of DAC		0	0	0	0
Interest expense		13	13	39	27
Other operating expenses		0	0	1	1
Total expenses		13	13	40	28
Income (loss) before income taxes		(13)	(13)	(40)	(28)
Total (provision) benefit for income taxes		5	4	14	9
Equity in net earnings of subsidiaries		126	290	594	529
Net income (loss)		118	281	568	510
Less: noncontrolling interest		0	0	0	0
Net income (loss)		118	281	568	510
Comprehensive income (loss)		138	294	482	650
Reportable Legal Entities [Member] | AGMH (Issuer) [Member]
Revenues
Net earned premiums		0	0	0	0
Net investment income		0	1	0	1
Net realized investment gains (losses)		0	0	1	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements		0	0	0	0
Net unrealized gains (losses)		0	0	0	0
Net change in fair value of credit derivatives		0	0	0	0
Bargain purchase gain and settlement of pre-existing relationships		0		0
Other		0	0	0	0
Total revenues		0	1	1	1
Expenses
Loss and LAE		0	0	0	0
Amortization of DAC		0	0	0	0
Interest expense		13	13	40	40
Other operating expenses		1	1	1	1
Total expenses		14	14	41	41
Income (loss) before income taxes		(14)	(13)	(40)	(40)
Total (provision) benefit for income taxes		5	5	14	14
Equity in net earnings of subsidiaries		133	147	347	436
Net income (loss)		124	139	321	410
Less: noncontrolling interest		0	0	0	0
Net income (loss)		124	139	321	410
Comprehensive income (loss)		139	146	269	495
Reportable Legal Entities [Member] | Other Entities [Member]
Revenues
Net earned premiums		219	142	585	408
Net investment income		113	104	318	307
Net realized investment gains (losses)		(22)	(19)	(13)	(23)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements		6	(14)	35	20
Net unrealized gains (losses)		81	269	292	127
Net change in fair value of credit derivatives		87	255	327	147
Bargain purchase gain and settlement of pre-existing relationships		0		54
Other		(16)	43	53	239
Total revenues		381	525	1,324	1,078
Expenses
Loss and LAE		114	(44)	316	48
Amortization of DAC		8	6	22	17
Interest expense		4	5	11	13
Other operating expenses		47	43	152	142
Total expenses		173	10	501	220
Income (loss) before income taxes		208	515	823	858
Total (provision) benefit for income taxes		(55)	(140)	(205)	(240)
Equity in net earnings of subsidiaries		10	8	30	24
Net income (loss)		163	383	648	642
Less: noncontrolling interest		10	24	30	24
Net income (loss)		153	359	618	618
Comprehensive income (loss)		199	397	554	957
Consolidating Adjustments [Member]
Revenues
Net earned premiums		(6)	2	(11)	4
Net investment income		(1)	(3)	(7)	(7)
Net realized investment gains (losses)		(5)	0	(8)	(2)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements		0	0	0	0
Net unrealized gains (losses)		(1)	0	(27)	0
Net change in fair value of credit derivatives		(1)	0	(27)	0
Bargain purchase gain and settlement of pre-existing relationships		0		160
Other		0	0	0	(1)
Total revenues		(13)	(1)	107	(6)
Expenses
Loss and LAE		(2)	0	2	6
Amortization of DAC		(3)	(2)	(7)	(5)
Interest expense		(5)	(4)	(14)	(13)
Other operating expenses		(1)	(2)	(2)	(3)
Total expenses		(11)	(8)	(21)	(15)
Income (loss) before income taxes		(2)	7	128	9
Total (provision) benefit for income taxes		2	(2)	(43)	(2)
Equity in net earnings of subsidiaries		(405)	(808)	(1,622)	(1,569)
Net income (loss)		(405)	(803)	(1,537)	(1,562)
Less: noncontrolling interest		(10)	(24)	(30)	(24)
Net income (loss)		(395)	(779)	(1,507)	(1,538)
Comprehensive income (loss)		$ (476)	$ (837)	$ (1,305)	$ (2,102)

[1] Excludes $6 million and $5 million for Third Quarter 2015 and 2014, respectively, and $16 million and $27 million for Nine Months 2015 and 2014, respectively, related to consolidated financial guaranty ("FG") VIEs.

[2] On October 9, 2015, the Company reached a settlement agreement with a CDS counterparty to terminate five Alt-A first lien CDS transactions. This termination agreement will generate a net fair value gain of approximately $293 million in the Company’s fourth quarter 2015 financial statements. In addition, on October 13, 2015, the Company terminated a CMBS transaction with a CDS counterparty and this termination agreement will generate a net fair value gain of approximately $34 million in the Company's fourth quarter 2015 financial statements.