Consolidated Balance Sheets - Successor [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets:
Fixed income securities, at fair value	$ 5,554,215	$ 5,043,776
Fixed income securities pledged as collateral, at fair value	64,905	64,555
Short-term investments, at fair value	430,788	225,789
Other investments	450,307	310,600
Total investments	6,500,215	5,644,720
Cash and cash equivalents	91,025	35,744
Receivable for securities	2,090	44,030
Investment income due and accrued	26,023	25,264
Premium receivables	661,337	831,575
Reinsurance recoverable on paid and unpaid losses	30,418	43,999
Deferred ceded premium	69,624	96,758
Subrogation recoverable	684,731	1,229,293
Loans	4,160	5,206
Derivative assets	77,742	84,995
Insurance intangible asset	962,080	1,212,112
Goodwill	0	0
Other assets	158,423	185,877
Total assets	22,635,702	23,728,070
Liabilities:
Unearned premiums	967,258	1,280,282
Loss and loss expense reserves	4,380,769	4,088,106
Ceded premiums payable	42,529	53,494
Obligations under investment agreements	82,358	100,358
Deferred Income Tax Liabilities, Net	1,720	2,205
Current taxes	14,280	5,835
Long-term debt	1,114,405	1,124,950
Accrued interest payable	421,975	355,536
Derivative liabilities	319,286	353,358
Other liabilities	76,589	61,134
Payable for securities purchased	1,084	84,690
Variable interest entity liabilities:
Total liabilities	20,657,678	21,769,724
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 20,000,000 shares authorized shares; issued and outstanding shares—none	0	0
Common stock, par value $0.01 per share; 130,000,000 shares authorized; issued and outstanding shares: 45,194,954 and 45,044,222	452	450
Additional paid-in capital	195,267	190,813
Accumulated other comprehensive income (loss)	(38,990)	15,215
Retained earnings	1,557,681	1,478,439
Treasury stock, shares at cost: 22,458 and 8,202	(496)	(118)
Total Ambac Financial Group, Inc. stockholders’ equity	1,713,914	1,684,799
Noncontrolling interest	264,110	273,547
Total stockholders’ equity	1,978,024	1,958,346
Total liabilities and stockholders’ equity	22,635,702	23,728,070
Variable Interest Entity [Member]
Assets:
Fixed income securities, at fair value	2,622,566	2,588,556
Derivative assets	80,407	0
Other assets	1,025	3,795
Variable interest entity assets:
Restricted cash	4,873	5,822
Loans, at fair value	10,658,963	11,690,324
Liabilities:
Long-term debt	11,155,936	12,327,960
Accrued interest payable	859	3,230
Derivative liabilities	2,078,601	1,928,403
Other liabilities	$ 29	$ 183