Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 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	46,014	45,450
Cash flows from operating activities:
Net income attributable to common shareholders	(171,630)	310,017
Net income (loss)	(171,630)	310,017
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	286	363
Amortization of bond premium and discount	(55,095)	(102,602)
Share-based compensation	7,365	8,765
Deferred income taxes	(809)	(880)
Current income taxes	33,000	(23,564)
Unearned premiums, net	(68,222)	(57,310)
Losses and loss expenses, net	(388,314)	(1,435,042)
Ceded premiums payable	(2,118)	(2,282)
Premium receivables	53,910	32,432
Accrued interest payable	42,396	(89,633)
Amortization of insurance intangible assets	262,520	51,878
Net mark-to-market (gains) losses	(598)	760
Net realized investment gains	(53,093)	(52,010)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, Net of Tax, Portion Attributable to Parent, Available-for-sale Securities	29	1,313
(Gain) loss on extinguishment of debt	0	(3,121)
Variable interest entity activities	(19,215)	(1,151)
Increase (Decrease) in Derivative Assets and Liabilities	(764)	(120)
Other, net	95,491	50,599
Net cash used in operating activities	(264,861)	(1,311,588)
Cash flows from investing activities:
Proceeds from sales of bonds	689,226	623,495
Proceeds from matured bonds	274,259	214,066
Purchases of bonds	(426,727)	(163,917)
Proceeds from sales of other invested assets	48,475	51,402
Purchases of other invested assets	(117,386)	(18,862)
Change in short-term investments	(342,091)	164,860
Change in cash collateral receivable	64,955	781
Proceeds From Financial Guaranty Variable Interest Entity Assets	122,085	137,983
Other, net	(221)	5,543
Net cash provided by investing activities	312,575	1,015,351
Cash flows from financing activities:
Proceeds From Issuance of Tier II Notes	0	240,000
Proceeds from Sale of Senior Surplus Notes	0	4,571
Paydown of Ambac Note	(21,914)	(113,457)
Paydowns of a secured borrowing	0	(73,993)
Paydown of Financial Guaranty Variable Interest Entity Liabilities	(92,042)	(137,984)
Payments for extinguishment of surplus notes	0	(191,258)
Payments of Debt Issuance Costs	0	(9,221)
AMPS Proceeds	18,818
Proceeds from Warrant Exercises	0	3
Payment, Tax Withholding, Share-based Payment Arrangement	(2,198)	(1,116)
Net cash used in financing activities	(85,156)	(282,455)
Effect of Exchange Rate on Cash and Cash Equivalents	(37)	(539)
Net cash flow	(37,479)	(579,231)
Cash, cash equivalents, and restricted cash at end of period	$ 17,514	$ 44,398