Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Statement of Cash Flows [Abstract]
Proceeds From Issuance of Ambac UK Debt	$ 12,180	$ 0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	67,680	53,529
Cash flows from operating activities:
Net income attributable to common shareholders	(105,514)	206,172
AMPS Exchange Loss Based on Carry Value	0	81,686
Net income (loss)	(105,514)	287,858
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	356	531
Amortization of bond premium and discount	(59,291)	(120,418)
Share-based compensation	9,699	10,475
Deferred income taxes	(3,292)	(6,121)
Current income taxes	27,849	(20,977)
Unearned premiums, net	(118,035)	(107,114)
Losses and loss expenses, net	(460,585)	(1,559,039)
Ceded premiums payable	(2,963)	(3,570)
Premium receivables	81,373	69,827
Accrued interest payable	64,847	(22,935)
Amortization of insurance intangible assets	279,941	78,299
Net mark-to-market (gains) losses	(1,037)	609
Net realized investment gains	(71,564)	(82,211)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Net of Tax, Portion Attributable to Parent, Available-for-sale Securities	71	1,579
(Gain) loss on extinguishment of debt	0	(3,121)
Variable interest entity activities	(30,459)	(2,982)
Increase (Decrease) in Derivative Assets and Liabilities	4,958	(38)
Other, net	87,415	61,405
Net cash used in operating activities	(296,231)	(1,417,943)
Cash flows from investing activities:
Proceeds from sales of bonds	1,051,990	1,091,516
Proceeds from matured bonds	316,818	292,395
Purchases of bonds	(866,087)	(348,682)
Proceeds from sales of other invested assets	72,558	111,524
Purchases of other invested assets	(134,948)	(93,800)
Change in short-term investments	(235,486)	(4,548)
Change in cash collateral receivable	75,018	10,953
Proceeds From Financial Guaranty Variable Interest Entity Assets	511,931	187,260
Other, net	(360)	2,742
Net cash provided by investing activities	791,434	1,249,360
Cash flows from financing activities:
Proceeds From Issuance of Tier II Notes	0	240,000
Proceeds from Sale of Senior Surplus Notes	0	17,714
Paydown of Ambac Note	(28,730)	(185,738)
Paydowns of a secured borrowing	0	(73,993)
Paydown of Financial Guaranty Variable Interest Entity Liabilities	(510,228)	(187,260)
Payments for extinguishment of surplus notes	0	(191,258)
Payments of Debt Issuance Costs	0	(9,221)
AMPS Exchange Cash Paid	0	(11,048)
AMPS Proceeds	18,818	0
Proceeds from Warrant Exercises	0	3
Payment, Tax Withholding, Share-based Payment Arrangement	(2,610)	(1,116)
Net cash used in financing activities	(510,570)	(401,917)
Effect of Exchange Rate on Cash and Cash Equivalents	(446)	(652)
Net cash flow	(15,813)	(571,152)
Cash, cash equivalents, and restricted cash at end of period	$ 51,951	$ 52,505