Financial Guarantee Insurance Contracts Financial Guarantee Insurance Contracts - Summary of Percentage Ceded to Reinsurers and Reinsurance Recoverable and Rating Levels (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Insurance [Abstract]
Loss Reserves Ceded To Reinsurers	$ 25,749	$ 22,623	$ 25,326	$ 40,658
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ 287	$ 510	$ 185