Reinsurance (Reinsurance amounts included in the Statements of Financial Position) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022		Sep. 30, 2022	Dec. 31, 2021	Jan. 01, 2021
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 36,860,011	$ 37,096,562	[1]
Policy loans	1,455,484	505,367
Deferred policy acquisition costs	6,923,554	6,930,425	[1]	$ 6,824,407	$ 7,029,307	$ 2,493,082
Deferred sales inducements	359,674	381,504	[1]
Market risk benefits assets	2,519,234	1,393,237	[1]	1,306,000
Other assets	2,029,917	1,331,427	[1]
Future policy benefits	21,257,134	20,829,033	[1]	20,003,692
Market risk benefit liabilities	4,371,178	5,521,601	[1]	$ 5,945,000
Other liabilities	4,720,229	3,597,373	[1]
Impacts of Reinsurance
Effects of Reinsurance [Line Items]
Reinsurance recoverables	36,860,011	37,096,562
Market risk benefits assets	1,108,690	543,177
Other assets	1,851,596	1,146,794
Policyholders' account balance	6,026,901	7,157,639
Future policy benefits	6,672,884	6,320,863
Market risk benefit liabilities	286,622	120,916
Other liabilities	4,039,544	2,891,433
Items Effected By Reinsurance Netting
Effects of Reinsurance [Line Items]
Policy loans	(1,073,903)	(1,011,112)
Deferred policy acquisition costs	(3,236,759)	(3,343,270)
Deferred sales inducements	(36,080)	(38,146)
Unaffiliated activity
Effects of Reinsurance [Line Items]
Deferred policy acquisition costs	74,341	111,379
Market risk benefits assets	757,038	64,738
Other assets	1,745,370	1,034,000
Policyholders' account balance	1,823,542	2,771,961
Future policy benefits	159	0
Market risk benefit liabilities	149,460	40,731
Other liabilities	$ 1,793,934	$ 820,185

[1] Prior period amounts adjusted for the implementation of Accounting Standard Update ("ASU") 2018-12: Targeted Improvements to the Accounting for Long-Duration Contracts.