Consolidated Balance Sheets - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Fixed income securities, at fair value (amortized cost of $4,825,555 and $5,435,385)	$ 4,978,118	$ 5,554,215
Fixed income securities pledged as collateral, at fair value (amortized cost of $99,424 and $64,833)	99,424	64,905
Short-term investments, at fair value (amortized cost of $716,666 and $430,827)	716,516	430,788
Other investments	439,987	450,307
Total investments	6,234,045	6,500,215
Cash and cash equivalents	107,018	91,025
Receivable for securities	68,686	2,090
Investment income due and accrued	20,137	26,023
Premium receivables	601,757	661,337
Reinsurance recoverable on paid and unpaid losses	45,976	30,418
Deferred ceded premium	54,773	69,624
Subrogation recoverable	703,930	684,731
Loans	10,390	4,160
Derivative assets	77,287	77,742
Insurance intangible asset	877,972	962,080
Other assets	48,228	158,423
Total assets	23,292,583	22,635,702
Liabilities:
Unearned premiums	817,538	967,258
Loss and loss expense reserves	4,704,285	4,380,769
Ceded premiums payable	38,593	42,529
Obligations under investment agreements	0	82,358
Obligations under investment agreements	(1,930)	(1,720)
Current taxes	18,484	14,280
Long-term debt	988,148	1,114,405
Accrued interest payable	417,522	421,975
Derivative Liability	90,899	319,286
Other liabilities	65,840	76,589
Payable for securities purchased	55,486	1,084
Total liabilities	21,520,446	20,657,678
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 20,000,000 shares authorized; issued and outstanding shares—none	0	0
Common Stock, Value, Issued	453	452
Additional paid-in capital	198,629	195,267
Accumulated other comprehensive income	62,680	(38,990)
Retained earnings	1,246,736	1,557,681
Treasury stock, shares at cost: 0 and 8,202	(471)	(496)
Total Ambac Financial Group, Inc. stockholders’ equity	1,508,027	1,713,914
Noncontrolling interest	264,110	264,110
Total stockholders’ equity	1,772,137	1,978,024
Total liabilities and stockholders’ equity	23,292,583	22,635,702
Deferred Income Tax Liabilities, Net	1,930	1,720
Variable Interest Entity [Member]
Assets:
Fixed income securities, at fair value (amortized cost of $4,825,555 and $5,435,385)	2,785,608	2,622,566
Restricted cash	37,793	4,873
Loans	11,557,788	10,658,963
Derivative assets	57,714	80,407
Other assets	3,481	1,025
Liabilities:
Long-term debt	12,229,569	11,155,936
Accrued interest payable	3,213	859
Derivative Liability	2,088,922	2,078,601
Other liabilities	$ 17	$ 29