Significant Accounting Policies and Pronouncements (Narratives) (Details)	Sep. 30, 2023 USD ($)	Jan. 01, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jan. 01, 2021 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	$ 3,816,917,000		$ 5,036,195,000
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net To Gross Ratio	1
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Balance after reinsurance recoverable, end of period, post-flooring	$ 0
Minimum | Deferred profit liability
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Balance after reinsurance recoverable, end of period, post-flooring	$ 0
Change of Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity		$ 673,000,000	$ 672,664,000	$ (271,000,000)