Subsidiary Information - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues
Net earned premiums	$ 219	$ 136	$ 361	$ 268
Net investment income	98	96	199	199
Net realized investment gains (losses)	(9)	(8)	7	(6)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	8	15	29	34
Net unrealized gains (losses)	82	88	185	(142)
Net change in fair value of credit derivatives	90	103	214	(108)
Bargain purchase gain and settlement of pre-existing relationships	214	0	214	0
Other	83	26	69	195
Total revenues	695	353	1,064	548
Expenses
Loss and LAE	188	57	206	98
Amortization of DAC	6	3	10	8
Interest expense	26	20	51	40
Other operating expenses	66	55	122	115
Total expenses	286	135	389	261
Income (loss) before income taxes	409	218	675	287
Total (provision) benefit for income taxes	(112)	(59)	(177)	(86)
Equity in net earnings of subsidiaries	0	0	0	0
Net income (loss)	297	159	498	201
Less: noncontrolling interest	0	0	0	0
Net income (loss)	297	159	498	201
Comprehensive income (loss)	166	227	367	373
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	9	8	17	16
Total expenses	9	8	17	16
Income (loss) before income taxes	(9)	(8)	(17)	(16)
Total (provision) benefit for income taxes	0	0	0	0
Equity in net earnings of subsidiaries	306	167	515	217
Net income (loss)	297	159	498	201
Less: noncontrolling interest	0	0	0	0
Net income (loss)	297	159	498	201
Comprehensive income (loss)	166	227	367	373
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	7	26	14
Other operating expenses	1	1	1	1
Total expenses	14	8	27	15
Income (loss) before income taxes	(14)	(8)	(27)	(15)
Total (provision) benefit for income taxes	4	3	9	5
Equity in net earnings of subsidiaries	305	152	468	239
Net income (loss)	295	147	450	229
Less: noncontrolling interest	0	0	0	0
Net income (loss)	295	147	450	229
Comprehensive income (loss)	210	191	344	356
Reportable Legal Entities [Member] | AGMH (Issuer) [Member]
Revenues
Net earned premiums	0	0	0	0
Net investment income	0	0	0	0
Net realized investment gains (losses)	1	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	1	0	1	0
Expenses
Loss and LAE	0	0	0	0
Amortization of DAC	0	0	0	0
Interest expense	14	14	27	27
Other operating expenses	0	0	0	0
Total expenses	14	14	27	27
Income (loss) before income taxes	(13)	(14)	(26)	(27)
Total (provision) benefit for income taxes	4	4	9	9
Equity in net earnings of subsidiaries	122	120	214	289
Net income (loss)	113	110	197	271
Less: noncontrolling interest	0	0	0	0
Net income (loss)	113	110	197	271
Comprehensive income (loss)	50	137	130	349
Reportable Legal Entities [Member] | Other Entities [Member]
Revenues
Net earned premiums	226	135	366	266
Net investment income	101	98	205	203
Net realized investment gains (losses)	(10)	(8)	9	(4)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	8	15	29	34
Net unrealized gains (losses)	108	88	211	(142)
Net change in fair value of credit derivatives	116	103	240	(108)
Bargain purchase gain and settlement of pre-existing relationships	54		54
Other	83	27	69	196
Total revenues	570	355	943	553
Expenses
Loss and LAE	184	53	202	92
Amortization of DAC	8	5	14	11
Interest expense	3	3	7	8
Other operating expenses	57	46	105	99
Total expenses	252	107	328	210
Income (loss) before income taxes	318	248	615	343
Total (provision) benefit for income taxes	(78)	(67)	(150)	(100)
Equity in net earnings of subsidiaries	11	8	20	16
Net income (loss)	251	189	485	259
Less: noncontrolling interest	11	16	20	16
Net income (loss)	240	173	465	243
Comprehensive income (loss)	122	302	355	560
Consolidating Adjustments [Member]
Revenues
Net earned premiums	(7)	1	(5)	2
Net investment income	(3)	(2)	(6)	(4)
Net realized investment gains (losses)	0	0	(3)	(2)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0	0	0
Net unrealized gains (losses)	(26)	0	(26)	0
Net change in fair value of credit derivatives	(26)	0	(26)	0
Bargain purchase gain and settlement of pre-existing relationships	160		160
Other	0	(1)	0	(1)
Total revenues	124	(2)	120	(5)
Expenses
Loss and LAE	4	4	4	6
Amortization of DAC	(2)	(2)	(4)	(3)
Interest expense	(4)	(4)	(9)	(9)
Other operating expenses	(1)	0	(1)	(1)
Total expenses	(3)	(2)	(10)	(7)
Income (loss) before income taxes	127	0	130	2
Total (provision) benefit for income taxes	(42)	1	(45)	0
Equity in net earnings of subsidiaries	(744)	(447)	(1,217)	(761)
Net income (loss)	(659)	(446)	(1,132)	(759)
Less: noncontrolling interest	(11)	(16)	(20)	(16)
Net income (loss)	(648)	(430)	(1,112)	(743)
Comprehensive income (loss)	$ (382)	$ (630)	$ (829)	$ (1,265)