Schedule II - Condensed Financial Information of Registrant (Parent Company Only) - Condensed Balance Sheet (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 01, 2013	Apr. 30, 2013
Condensed Balance Sheet Statements, Captions [Line Items]
Tolling Payment Payable to AFG	$ 70,911
Assets:
Junior surplus note of Ambac Assurance Segregated Account				$ 350,000	$ 350,000
Total assets					28,853,435
Liabilities:
Total liabilities					28,393,020
Stockholders' equity (deficit):
Common stock					450
Additional paid-in capital					184,550
Successor [Member]
Assets:
Available-for-sale Securities, Debt Securities	5,043,776	$ 4,725,686
Other investments	310,600	357,016
Total investments	5,644,720	5,507,034			6,457,264
Cash					152,951
Investment income due and accrued	25,264	25,015			37,961
Other assets	185,877	186,985			54,821
Total assets	23,728,070	25,159,864	$ 27,092,477		28,853,435
Liabilities:
Current taxes	5,835	5,701			0
Total liabilities	21,769,724	23,486,129			28,393,020
Stockholders' equity (deficit):
Preferred stock	0	0			0
Common stock	450	450			450
Additional paid-in capital	190,813	189,138
Accumulated other comprehensive income	15,215	220,283	$ 11,661		0
Retained earnings (accumulated deficit)	1,478,439	989,290			0
Common stock held in treasury at cost	(118)	(56)			0
Total Ambac Financial Group, Inc. stockholders’ equity	1,684,799	1,399,105			185,000
Total liabilities and stockholders’ equity	23,728,070	25,159,864			28,853,435
Predecessor [Member]
Assets:
Total investments					6,457,264
Cash					254,851
Investment income due and accrued					37,961
Other assets					54,821
Total assets					28,853,435
Liabilities:
Current taxes					97,490
Total liabilities					29,444,265
Stockholders' equity (deficit):
Preferred stock					0
Accumulated other comprehensive income					800,260
Retained earnings (accumulated deficit)					(5,697,961)
Common stock held in treasury at cost					$ 410,695
Ambac Financial Group, Inc Parent Company Only [Member] | Successor [Member]
Assets:
Available-for-sale Securities, Debt Securities	187,979	234,310
Short-term investments, at cost (approximates fair value)	48,079	22,936
Other investments	25,339	21,003
Total investments	261,397	278,249
Cash	25	141
Investment in subsidiaries	1,349,483	1,116,044
Investment income due and accrued	123	54
Related Party Tax Expense, Due from Affiliates, Current	70,848
Other assets	4,778	5,770
Total assets	1,686,654	1,400,258
Liabilities:
Current taxes	0	221
Accounts payable and other liabilities	1,855	932
Total liabilities	1,855	1,153
Stockholders' equity (deficit):
Preferred stock	0	0
Common stock	450	450
Additional paid-in capital	190,813	189,138
Accumulated other comprehensive income	15,215	220,283
Retained earnings (accumulated deficit)	1,478,439	989,290
Common stock held in treasury at cost	(118)	(56)
Total Ambac Financial Group, Inc. stockholders’ equity	1,684,799	1,399,105
Total liabilities and stockholders’ equity	$ 1,686,654	$ 1,400,258