Subsidiary Information - Condensed Consolidating Statement of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Revenues
Net earned premiums	$ 142	$ 132
Net investment income	101	103
Net realized investment gains (losses)	16	2
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	21	19
Net unrealized gains (losses)	103	(230)
Net change in fair value of credit derivatives	124	(211)
Other	(14)	169
Total revenues	369	195
Expenses
Loss and LAE	18	41
Amortization of DAC	4	5
Interest expense	25	20
Other operating expenses	56	60
Total expenses	103	126
Income (loss) before income taxes	266	69
Total (provision) benefit for income taxes	(65)	(27)
Equity in net earnings of subsidiaries	0	0
Net income (loss)	201	42
Less: noncontrolling interest	0	0
Net income (loss)	201	42
Comprehensive income (loss)	201	146
Reportable Legal Entities [Member] | Assured Guaranty Ltd. (Parent) [Member]
Revenues
Net earned premiums	0	0
Net investment income	0	0
Net realized investment gains (losses)	0	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0
Net unrealized gains (losses)	0	0
Net change in fair value of credit derivatives	0	0
Other	0	0
Total revenues	0	0
Expenses
Loss and LAE	0	0
Amortization of DAC	0	0
Interest expense	0	0
Other operating expenses	8	8
Total expenses	8	8
Income (loss) before income taxes	(8)	(8)
Total (provision) benefit for income taxes	0	0
Equity in net earnings of subsidiaries	209	50
Net income (loss)	201	42
Less: noncontrolling interest	0	0
Net income (loss)	201	42
Comprehensive income (loss)	201	146
Reportable Legal Entities [Member] | AGUS (Issuer) [Member]
Revenues
Net earned premiums	0	0
Net investment income	0	0
Net realized investment gains (losses)	0	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0
Net unrealized gains (losses)	0	0
Net change in fair value of credit derivatives	0	0
Other	0	0
Total revenues	0	0
Expenses
Loss and LAE	0	0
Amortization of DAC	0	0
Interest expense	13	7
Other operating expenses	0	0
Total expenses	13	7
Income (loss) before income taxes	(13)	(7)
Total (provision) benefit for income taxes	5	2
Equity in net earnings of subsidiaries	163	87
Net income (loss)	155	82
Less: noncontrolling interest	0	0
Net income (loss)	155	82
Comprehensive income (loss)	134	165
Reportable Legal Entities [Member] | AGMH (Issuer) [Member]
Revenues
Net earned premiums	0	0
Net investment income	0	0
Net realized investment gains (losses)	0	0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0
Net unrealized gains (losses)	0	0
Net change in fair value of credit derivatives	0	0
Other	0	0
Total revenues	0	0
Expenses
Loss and LAE	0	0
Amortization of DAC	0	0
Interest expense	13	13
Other operating expenses	0	0
Total expenses	13	13
Income (loss) before income taxes	(13)	(13)
Total (provision) benefit for income taxes	5	5
Equity in net earnings of subsidiaries	92	169
Net income (loss)	84	161
Less: noncontrolling interest	0	0
Net income (loss)	84	161
Comprehensive income (loss)	80	212
Reportable Legal Entities [Member] | Other Entities [Member]
Revenues
Net earned premiums	140	131
Net investment income	104	105
Net realized investment gains (losses)	19	4
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	21	19
Net unrealized gains (losses)	103	(230)
Net change in fair value of credit derivatives	124	(211)
Other	(14)	169
Total revenues	373	198
Expenses
Loss and LAE	18	39
Amortization of DAC	6	6
Interest expense	4	5
Other operating expenses	48	53
Total expenses	76	103
Income (loss) before income taxes	297	95
Total (provision) benefit for income taxes	(72)	(33)
Equity in net earnings of subsidiaries	9	8
Net income (loss)	234	70
Less: noncontrolling interest	9	8
Net income (loss)	225	62
Comprehensive income (loss)	233	258
Consolidating Adjustments [Member]
Revenues
Net earned premiums	2	1
Net investment income	(3)	(2)
Net realized investment gains (losses)	(3)	(2)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements	0	0
Net unrealized gains (losses)	0	0
Net change in fair value of credit derivatives	0	0
Other	0	0
Total revenues	(4)	(3)
Expenses
Loss and LAE	0	2
Amortization of DAC	(2)	(1)
Interest expense	(5)	(5)
Other operating expenses	0	(1)
Total expenses	(7)	(5)
Income (loss) before income taxes	3	2
Total (provision) benefit for income taxes	(3)	(1)
Equity in net earnings of subsidiaries	(473)	(314)
Net income (loss)	(473)	(313)
Less: noncontrolling interest	(9)	(8)
Net income (loss)	(464)	(305)
Comprehensive income (loss)	$ (447)	$ (635)