Schedule II - Condensed Financial Information of Registrant (Parent Company Only) - Condensed Statements of Cash Flows (Detail) - USD ($)	3 Months Ended								4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Apr. 30, 2013	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Condensed Cash Flow Statements, Captions [Line Items]
Junior Surplus Notes To Be Issued									$ (350,000,000)
Successor [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Other-than-temporary impairment charges										$ 46,764,000	$ 25,659,000	$ 25,794,000
Cash flows from operating activities:
Net income (loss)										504,802,000	492,694,000	483,696,000
Adjustments to reconcile net income loss to net cash used in operating activities:
Accretion (Amortization) of Discounts and Premiums, Investments										(34,698,000)	(129,584,000)	(79,183,000)
Reorganization items	$ 0	$ 0	$ 0	$ 0	$ 0	$ 2,000	$ 186,000	$ 23,000		493,000	0	211,000
Net realized investment gains										(4,467,000)	(53,476,000)	(58,777,000)
Decrease in current income taxes payable										5,148,000	134,000	4,963,000
Share-based compensation										1,106,000	3,105,000	3,450,000
Investment income due and accrued										298,000	(249,000)	12,648,000
Other, net										(137,150,000)	80,988,000	152,846,000
Net cash provided by (used in) operating activities										186,908,000	87,542,000	(971,509,000)
Cash flows from investing activities:
Proceeds from matured bonds										613,345,000	1,029,026,000	1,402,904,000
Purchases of bonds										(2,213,116,000)	(2,374,804,000)	(2,937,782,000)
Change in short-term investments										455,495,000	134,276,000	(88,946,000)
Net cash provided by (used in) investing activities										(247,510,000)	(172,602,000)	1,275,153,000
Proceeds from the sale of Junior Surplus Notes of the Segregated Account										0	0	224,262,000
Payments for Repurchase of Warrants										0	5,375,000	0
Cash flows from financing activities:
Paydowns of a secured borrowing										16,000	3,000	16,000
Payments for investment agreement draws										(14,979,000)	46,901,000	(307,111,000)
Payments for extinguishment of long-term debt										(75,581,000)	(38,159,000)	(3,467,000)
Cash and cash equivalents at beginning of period				73,903,000				77,370,000		152,951,000	73,903,000	77,370,000
Cash and cash equivalents end of period	35,744,000				73,903,000				152,951,000	77,370,000	35,744,000	73,903,000
Cash paid during the period for:
Income taxes										1,656,000	16,969,000	4,400,000
Professional fees paid for services rendered in connection with the Chapter 11 proceeding										15,546,000	0	272,000
Predecessor [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Other-than-temporary impairment charges									467,000
Cash flows from operating activities:
Net income (loss)									3,347,278,000
Adjustments to reconcile net income loss to net cash used in operating activities:
Accretion (Amortization) of Discounts and Premiums, Investments									(60,146,000)
Reorganization items									(2,745,180,000)
Net realized investment gains									(53,305,000)
Decrease in current income taxes payable									(101,188,000)
Share-based compensation									0
Investment income due and accrued									1,781,000
Other, net									62,122,000
Net cash provided by (used in) operating activities									(683,000)
Cash flows from investing activities:
Proceeds from matured bonds									307,472,000
Purchases of bonds									(286,633,000)
Change in short-term investments									(64,956,000)
Net cash provided by (used in) investing activities									115,316,000
Proceeds from the sale of Junior Surplus Notes of the Segregated Account									0
Payments for Repurchase of Warrants									0
Cash flows from financing activities:
Paydowns of a secured borrowing									0
Payments for investment agreement draws									(5,519,000)
Payments for extinguishment of long-term debt									109,114,000
Cash and cash equivalents at beginning of period									43,837,000	152,951,000
Cash and cash equivalents end of period									152,951,000
Cash paid during the period for:
Income taxes									102,129,000
Professional fees paid for services rendered in connection with the Chapter 11 proceeding									3,860,000
Ambac Financial Group, Inc Parent Company Only [Member] | Successor [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Junior Surplus Notes To Be Issued	0				0					(167,020,000)	0	0
Other-than-temporary impairment charges											155,000
Cash flows from operating activities:
Net income (loss)										505,219,000	493,403,000	484,071,000
Adjustments to reconcile net income loss to net cash used in operating activities:
Equity in undistributed net (income) loss of non-debtor subsidiaries										(289,379,000)	(421,870,000)	(465,860,000)
Accretion (Amortization) of Discounts and Premiums, Investments											(4,690,000)	4,000
Reorganization items										493,000	0	211,000
Net realized investment gains										(2,000)	27,000	46,000
Decrease in current income taxes payable										0	(71,069,000)	221,000
Share-based compensation										1,106,000	3,105,000	3,450,000
Investment income due and accrued										(11,942,000)	(69,000)	11,905,000
Decrease in other assets										(1,677,000)	992,000	(834,000)
Other, net										(28,030,000)	(4,705,000)	(36,628,000)
Net cash provided by (used in) operating activities										8,768,000	(4,721,000)	(3,414,000)
Cash flows from investing activities:
Proceeds from matured bonds										14,355,000	347,539,000	65,032,000
Purchases of bonds										(42,506,000)	(312,419,000)	(271,181,000)
Change in short-term investments										19,360,000	(25,143,000)	(14,617,000)
Net cash provided by (used in) investing activities										(8,791,000)	9,977,000	(220,766,000)
Proceeds from the sale of Junior Surplus Notes of the Segregated Account										0	0	224,262,000
Payments for Repurchase of Warrants											(5,375,000)
Cash flows from financing activities:
Paydowns of a secured borrowing										16,000	3,000	16,000
Payments for investment agreement draws										16,000	(5,372,000)	224,278,000
Payments for extinguishment of long-term debt										(7,000)	(116,000)	98,000
Cash and cash equivalents at beginning of period				$ 141,000				$ 43,000		50,000	141,000	43,000
Cash and cash equivalents end of period	$ 25,000				$ 141,000				50,000	43,000	25,000	141,000
Cash paid during the period for:
Income taxes										0	394,000	0
Professional fees paid for services rendered in connection with the Chapter 11 proceeding										15,546,000	$ 0	$ 272,000
Ambac Financial Group, Inc Parent Company Only [Member] | Predecessor [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Junior Surplus Notes To Be Issued									0
Cash flows from operating activities:
Net income (loss)									3,349,049,000
Adjustments to reconcile net income loss to net cash used in operating activities:
Equity in undistributed net (income) loss of non-debtor subsidiaries									(603,666,000)
Reorganization items									(2,745,180,000)
Net realized investment gains									0
Decrease in current income taxes payable									(1,900,000)
Share-based compensation									0
Investment income due and accrued									(6,000)
Decrease in other assets									3,182,000
Other, net									(4,107,000)
Net cash provided by (used in) operating activities									(2,628,000)
Cash flows from investing activities:
Proceeds from matured bonds									0
Purchases of bonds									0
Change in short-term investments									2,637,000
Net cash provided by (used in) investing activities									2,637,000
Proceeds from the sale of Junior Surplus Notes of the Segregated Account									0
Cash flows from financing activities:
Paydowns of a secured borrowing									0
Payments for investment agreement draws									0
Payments for extinguishment of long-term debt									9,000
Cash and cash equivalents at beginning of period									41,000	$ 50,000
Cash and cash equivalents end of period									50,000
Cash paid during the period for:
Income taxes									1,900,000
Professional fees paid for services rendered in connection with the Chapter 11 proceeding									$ 3,860,000