Financial Guarantee Insurance Contracts Financial Guarantee Insurance Contracts - Components of Loss and Loss Expense Reserves and Subrogation Recoverable (Details) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ (418)	$ (162)	$ (349)
Loss Reserves Ceded To Reinsurers	34,691	27,478	30,767	$ 44,059
Policyholder Benefits and Claims Incurred, Ceded	(4,112)	(9,454)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	3,795,664	$ 3,615,598	3,665,271	$ 2,814,754
Loss and loss expense reserves	4,510,329		4,380,769
Subrogation recoverable	(679,974)		(684,731)
Claim liability reported on Balance Sheet, before reinsurance	3,830,355		3,696,038
Unpaid Claims-Claims [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	2,406,397		2,411,105
Subrogation recoverable	581,979		583,042
Claim liability reported on Balance Sheet, before reinsurance	2,988,376		2,994,147
Unpaid Claims-Accrued Interest [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	565,369		529,703
Subrogation recoverable	140,242		132,139
Claim liability reported on Balance Sheet, before reinsurance	705,611		661,842
Present Value of Expected Net Cash Flows- Claims and Loss Expenses [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	2,862,877		2,681,198
Subrogation recoverable	44,638		68,419
Claim liability reported on Balance Sheet, before reinsurance	2,907,515		2,749,617
Present Value of Expected Net Cash Flows-Recoveries [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	(1,182,839)		(1,098,096)
Subrogation recoverable	(1,446,833)		(1,468,331)
Claim liability reported on Balance Sheet, before reinsurance	(2,629,672)		(2,566,427)
Unearned Premium Reserve [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	(141,475)		(143,141)
Subrogation recoverable	0		0
Claim liability reported on Balance Sheet, before reinsurance	$ (141,475)		$ (143,141)

Financial Guarantee Insurance Contracts Financial Guarantee Insurance Contracts - Components of Loss and Loss Expense Reserves and Subrogation Recoverable (Details) - Successor [Member] - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2017

Mar. 31, 2016

Dec. 31, 2016

Dec. 31, 2015

Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]

Ceded Loss And Loss Expenses Paid Not Yet Recovered

$ (418)

$ (162)

$ (349)

Loss Reserves Ceded To Reinsurers

34,691