New Accounting Standards - Liability For Future Policy Benefits To Consolidated Statements of Shareholders' Equity: (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Liability for Future Policy Benefit, Activity [Line Items]
Stockholders' equity	$ 3,846,291	$ 3,949,577	$ 2,544,275	$ 2,003,808	$ 933,521	$ 8,771,092
Cumulative Effect, Period of Adoption, Adjustment
Liability for Future Policy Benefit, Activity [Line Items]
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
Retained Earnings
Liability for Future Policy Benefit, Activity [Line Items]
Stockholders' equity	7,092,544	6,894,535	6,662,365	6,455,733	5,861,587	5,874,109
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
Liability for Future Policy Benefit, Activity [Line Items]
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
Accumulated Other Comprehensive Income (Loss)
Liability for Future Policy Benefit, Activity [Line Items]
Stockholders' equity	$ (2,961,093)	$ (2,790,313)	$ (3,827,006)	$ (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, Activity [Line Items]
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
Other
Liability for Future Policy Benefit, Activity [Line Items]
Stockholders' equity					$ (132,261)	(132,261)
Other | Cumulative Effect, Period of Adoption, Adjustment
Liability for Future Policy Benefit, Activity [Line Items]
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