Business and Basis of Presentation (Liability for Future Policy Benefit-Benefits Reserve) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance after transition, at current discount rate	$ 17,216,882		$ 17,684,170
Benefit Reserves
Liability for Future Policy Benefit, Activity [Line Items]
Balance					$ 8,522,254
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance after transition, at current discount rate					14,299,073
Reinsurance recoverable					13,728,627
Balance after reinsurance recoverable, end of period, post-flooring					570,446
As Previously Reported | Benefit Reserves
Liability for Future Policy Benefit, Activity [Line Items]
Balance						$ 8,486,563
Changes in cash flow assumptions and other activity | Benefit Reserves
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Cash flow change					35,691
Cumulative changes in discount rate assumptions | Benefit Reserves
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Cash flow change					5,776,819
Term Life
Liability for Future Policy Benefit, Activity [Line Items]
Balance	18,771,355	$ 18,797,285	18,853,526	$ 17,329,822
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance after transition, at current discount rate	17,003,374	$ 17,835,251	17,482,881	$ 20,937,097
Reinsurance recoverable	6,241,505		6,293,473
Balance after reinsurance recoverable, end of period, post-flooring	$ 485,858		$ 363,808
Term Life | Benefit Reserves
Liability for Future Policy Benefit, Activity [Line Items]
Balance					6,674,231
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance after transition, at current discount rate					9,106,241
Reinsurance recoverable					8,536,200
Balance after reinsurance recoverable, end of period, post-flooring					570,041
Term Life | As Previously Reported | Benefit Reserves
Liability for Future Policy Benefit, Activity [Line Items]
Balance						6,674,490
Term Life | Changes in cash flow assumptions and other activity | Benefit Reserves
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Cash flow change					(259)
Term Life | Cumulative changes in discount rate assumptions | Benefit Reserves
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Cash flow change					2,432,010
Life Insurance - Taiwan | Benefit Reserves
Liability for Future Policy Benefit, Activity [Line Items]
Balance					1,635,562
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance after transition, at current discount rate					4,952,553
Reinsurance recoverable					4,952,553
Balance after reinsurance recoverable, end of period, post-flooring					0
Life Insurance - Taiwan | As Previously Reported | Benefit Reserves
Liability for Future Policy Benefit, Activity [Line Items]
Balance						1,592,329
Life Insurance - Taiwan | Changes in cash flow assumptions and other activity | Benefit Reserves
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Cash flow change					43,233
Life Insurance - Taiwan | Cumulative changes in discount rate assumptions | Benefit Reserves
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Cash flow change					3,316,991
Other | Benefit Reserves
Liability for Future Policy Benefit, Activity [Line Items]
Balance					212,461
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance after transition, at current discount rate					240,279
Reinsurance recoverable					239,874
Balance after reinsurance recoverable, end of period, post-flooring					405
Other | As Previously Reported | Benefit Reserves
Liability for Future Policy Benefit, Activity [Line Items]
Balance						$ 219,744
Other | Changes in cash flow assumptions and other activity | Benefit Reserves
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Cash flow change					(7,283)
Other | Cumulative changes in discount rate assumptions | Benefit Reserves
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Cash flow change					$ 27,818