Significant Accounting Policies - Schedule of Liability For Future Policy Benefits To Consolidated Statements of Shareholders' Equity: (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Shareholders’ Equity, as of December 31, 2020	$ 4,486,803	$ 3,949,577	$ 2,003,808	$ 933,521	$ 8,771,092
Shareholders’ Equity, as of January 1, 2021	4,486,803	3,949,577	2,003,808	933,521	8,771,092
Cumulative Effect, Period of Adoption, Adjustment
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Shareholders’ Equity, as of December 31, 2020					(7,837,571)
Effect of changes in discount rate assumptions					(7,829,753)
Effect of capping and flooring					(38,992)
Effect of removal of unrealized gain (loss) on DAC					4,704
Other adjustments					26,470
Shareholders’ Equity, as of January 1, 2021					(7,837,571)
Retained Earnings
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Shareholders’ Equity, as of December 31, 2020	7,478,813	6,894,535	6,455,733	5,861,587	5,874,109
Shareholders’ Equity, as of January 1, 2021	7,478,813	6,894,535	6,455,733	5,861,587	5,874,109
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Shareholders’ Equity, as of December 31, 2020					(12,522)
Effect of changes in discount rate assumptions					0
Effect of capping and flooring					(38,992)
Effect of removal of unrealized gain (loss) on DAC					0
Other adjustments					26,470
Shareholders’ Equity, as of January 1, 2021					(12,522)
Accumulated Other Comprehensive Income (Loss)
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Shareholders’ Equity, as of December 31, 2020	(2,772,419)	(2,790,313)	(4,235,048)	(4,795,805)	3,029,244
Shareholders’ Equity, as of January 1, 2021	$ (2,772,419)	$ (2,790,313)	$ (4,235,048)	(4,795,805)	3,029,244
Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjustment
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Shareholders’ Equity, as of December 31, 2020					(7,825,049)
Effect of changes in discount rate assumptions					(7,829,753)
Effect of capping and flooring					0
Effect of removal of unrealized gain (loss) on DAC					4,704
Other adjustments					0
Shareholders’ Equity, as of January 1, 2021					(7,825,049)
Other
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Shareholders’ Equity, as of December 31, 2020				(132,261)	(132,261)
Shareholders’ Equity, as of January 1, 2021				$ (132,261)	(132,261)
Other | Cumulative Effect, Period of Adoption, Adjustment
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Effect of changes in discount rate assumptions					0
Effect of capping and flooring					0
Effect of removal of unrealized gain (loss) on DAC					0
Other adjustments					$ 0