Consolidated Statements of Cash Flows - Successor [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income attributable to common shareholders	$ 74,843	$ 493,403	$ 484,071
Net (loss) gain	526	709	375
Net income (loss)	74,317	492,694	483,696
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	1,220	3,215	3,582
Goodwill, Impairment Loss	0	514,511	0
Amortization of bond premium and discount	(150,061)	(129,584)	(79,183)
Reorganization items	0	0	211
Share-based compensation	5,253	3,104	3,450
Deferred income taxes	(485)	126	(120)
Current income taxes	9,727	134	4,963
Unearned premiums, net	(289,140)	(372,907)	(576,018)
Losses and loss expenses, net	853,978	(799,399)	(1,652,854)
Ceded premiums payable	(10,965)	(6,942)	(10,526)
Investment income due and accrued	(750)	(280)	12,647
Premium receivables	172,331	174,918	470,191
Accrued interest payable	66,439	51,397	9,322
Amortization of insurance intangible assets	174,608	169,557	151,830
Net mark-to-market (gains) losses	(19,194)	(38,916)	(20,863)
Net realized investment gains	(39,284)	(53,476)	(58,777)
Other-than-temporary impairment charges	21,819	25,659	25,794
Net realized gains (losses) on extinguishment of debt	(4,845)	(81)	74,724
Variable interest entity activities	14,093	(31,569)	32,212
Other, net	(35,521)	89,648	157,899
Net cash provided by (used in) operating activities	843,540	91,809	(967,820)
Cash flows from investing activities:
Proceeds from sales of bonds	867,882	996,427	3,120,592
Proceeds from matured bonds	1,317,215	1,029,026	1,402,904
Purchases of bonds	(2,574,285)	(2,374,441)	(2,937,744)
Proceeds from sales of other invested assets	131,703	178,474	49,271
Purchases of other invested assets	(281,570)	(128,186)	(133,928)
Change in short-term investments	(206,002)	134,423	(87,554)
Loans, net	1,046	508	465
Change in cash collateral receivable	27,372	(6,833)	(153,853)
Other, net	1,996	(5,143)	11,574
Net cash provided by (used in) investing activities	(714,643)	(175,745)	1,271,727
Cash flows from financing activities:
Proceeds from the sale of Junior Surplus Notes of the Segregated Account	0	0	224,262
Proceeds Received from a Secured Borrowing	0	(143,430)	0
Paydown Of Variable Interest Entity Secured Borrowing	29,482	13,533	0
Payments From Drawdowns Of Borrowings Under Guaranteed Investment Agreements	17,964	63,872	199,970
Payments for extinguishment of long-term debt	(19,550)	(13,752)	(331,419)
Proceeds from Warrant Exercises	2	3	16
Payments for Repurchase of Warrants	(2,717)	(5,375)	0
Net Cash Provided by (Used in) Financing Activities	(69,711)	46,901	(307,111)
Effect of Exchange Rate on Cash and Cash Equivalents	(3,905)	(1,124)	(263)
Cash and Cash Equivalents, Period Increase (Decrease)	55,281	(38,159)	(3,467)
Cash and cash equivalents at beginning of period	35,744	73,903	77,370
Cash and cash equivalents end of period	91,025	35,744	73,903
Supplemental disclosure of cash flow information
Income taxes	21,437	16,969	4,400
Interest on investment agreements	614	341	518
Cash payments related to reorganization items:
Professional fees paid for services rendered in connection with the Chapter 11 proceeding	0	0	272
Surplus Notes [Member]
Supplemental disclosure of cash flow information
Interest on surplus notes	0	0	82,168
Variable Interest Entity [Member] | Secured Borrowing [Member]
Supplemental disclosure of cash flow information
Interest on secured borrowing	3,923	1,506	0
Ambac Financial Group, Inc Parent Company Only [Member]
Cash flows from operating activities:
Net income (loss)	74,843	493,403	484,071
Adjustments to reconcile net income to net cash used in operating activities:
Amortization of bond premium and discount	(7,208)	(4,690)	4
Reorganization items	0	0	211
Share-based compensation	5,253	3,105	3,450
Current income taxes	42,126	(71,069)	221
Investment income due and accrued	(149)	(69)	11,905
Net realized investment gains	7	27	46
Other-than-temporary impairment charges	289	155	0
Other, net	5,814	(4,705)	(36,628)
Net cash provided by (used in) operating activities	77,228	(4,721)	(3,414)
Cash flows from investing activities:
Proceeds from matured bonds	269,459	347,539	65,032
Purchases of bonds	(279,582)	(312,419)	(271,181)
Change in short-term investments	(18,491)	(25,143)	(14,617)
Net cash provided by (used in) investing activities	(42,287)	9,977	(220,766)
Cash flows from financing activities:
Proceeds from the sale of Junior Surplus Notes of the Segregated Account	0	0	224,262
Proceeds from Warrant Exercises	2	3	16
Payments for Repurchase of Warrants	2,717	5,375	0
Net Cash Provided by (Used in) Financing Activities	(2,715)	(5,372)	224,278
Cash and Cash Equivalents, Period Increase (Decrease)	32,226	(116)	98
Cash and cash equivalents at beginning of period	25	141	43
Cash and cash equivalents end of period	32,251	25	141
Supplemental disclosure of cash flow information
Income taxes	0	394	0
Cash payments related to reorganization items:
Professional fees paid for services rendered in connection with the Chapter 11 proceeding	$ 0	$ 0	$ 272