Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022		Jun. 30, 2022
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	$ 23,441,750	$ 19,025,401
Market risk benefits assets	2,340,230	1,393,237	[1]	$ 1,423,000
Fixed maturities, trading	2,477,679	1,936,159
Equity securities	379,574	143,072
Other invested assets	1,207,395	1,088,613
Other assets	1,787,731	1,331,427	[1]
Reinsurance recoverables	37,667,480	37,096,562	[1]
Receivables from parent and affiliates	267,218	224,921
Separate account assets	117,840,155	114,051,246
TOTAL ASSETS	205,566,500	193,473,118
Market risk benefit liabilities	5,089,766	5,521,601	[1]	$ 6,686,000
Payables to parent and affiliates	2,370,004	2,126,571
Other liabilities	4,540,528	3,597,373	[1]
Total liabilities	199,895,847	188,436,923
Fair Value, Measurements, Recurring
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	23,441,750	19,025,401
Market risk benefits assets	2,340,230	1,393,237
Fixed maturities, trading	2,477,679	1,936,159
Equity securities	379,574	143,072
Short-term investments	239,607	98,160
Cash equivalents	1,092,394	1,432,182
Other invested assets	96,731	47,111
Other assets	217,613	141,041
Reinsurance recoverables	1,465	0
Receivables from parent and affiliates	145,661	148,075
Subtotal excluding separate account assets	30,432,704	24,364,438
Separate account assets	113,035,272	108,789,313
TOTAL ASSETS	143,467,976	133,153,751
Market risk benefit liabilities	5,089,766	5,521,601
Policyholders’ account balances	5,513,449	3,502,096
Payables to parent and affiliates	2,354,472	2,084,917
Other liabilities	(18,307)	(9,267)
Total liabilities	12,939,380	11,099,347
Assets netting	(8,201,896)	(7,637,939)
Liabilities netting	(17,405,225)	(16,568,912)
Netting	(9,203,000)	(8,931,000)
Fair Value, Measurements, Recurring | Other invested assets
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets netting	(8,201,896)	(7,637,939)
Fair Value, Measurements, Recurring | Payables to parent and affiliates
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities netting	(17,404,023)	(16,568,242)
Fair Value, Measurements, Recurring | Other liabilities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities netting	(1,202)	(670)
Fair Value, Measurements, Recurring | U.S. Treasury securities and obligations of U.S. government authorities and agencies
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	324,261	281,792
Fair Value, Measurements, Recurring | Obligations of U.S. states and their political subdivisions
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	777,091	628,200
Fair Value, Measurements, Recurring | Foreign government bonds
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	288,308	273,462
Fair Value, Measurements, Recurring | U.S. corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	8,884,883	6,443,944
Fair Value, Measurements, Recurring | U.S. corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	4,327,905	3,816,729
Fair Value, Measurements, Recurring | Foreign corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	1,719,452	1,378,222
Fair Value, Measurements, Recurring | Foreign corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	4,039,723	3,766,330
Fair Value, Measurements, Recurring | Asset-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	1,897,566	1,442,354
Fair Value, Measurements, Recurring | Commercial mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	780,105	658,152
Fair Value, Measurements, Recurring | Residential mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	402,456	336,216
Fair Value, Measurements, Recurring | Level 1
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Market risk benefits assets	0	0
Fixed maturities, trading	0	0
Equity securities	145,759	108,076
Short-term investments	49,804	0
Cash equivalents	0	0
Other invested assets	95,126	4,223
Other assets	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	290,689	112,299
Separate account assets	114,988	102,243
TOTAL ASSETS	405,677	214,542
Market risk benefit liabilities	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	0	0
Other liabilities	8,448	899
Total liabilities	8,448	899
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury securities and obligations of U.S. government authorities and agencies
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Obligations of U.S. states and their political subdivisions
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Foreign government bonds
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | U.S. corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | U.S. corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Foreign corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Foreign corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Asset-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Commercial mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Residential mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	22,573,463	18,412,457
Market risk benefits assets	0	0
Fixed maturities, trading	2,477,679	1,936,159
Equity securities	190,441	6,403
Short-term investments	188,594	81,215
Cash equivalents	1,092,394	1,432,182
Other invested assets	8,203,501	7,680,827
Other assets	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	145,661	148,075
Subtotal excluding separate account assets	34,871,733	29,697,318
Separate account assets	112,915,302	108,682,425
TOTAL ASSETS	147,787,035	138,379,743
Market risk benefit liabilities	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	19,758,495	18,653,159
Other liabilities	(25,553)	(9,496)
Total liabilities	19,732,942	18,643,663
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury securities and obligations of U.S. government authorities and agencies
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	324,261	281,792
Fair Value, Measurements, Recurring | Level 2 | Obligations of U.S. states and their political subdivisions
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	777,091	628,200
Fair Value, Measurements, Recurring | Level 2 | Foreign government bonds
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	287,607	272,738
Fair Value, Measurements, Recurring | Level 2 | U.S. corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	8,884,883	6,443,944
Fair Value, Measurements, Recurring | Level 2 | U.S. corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	3,989,251	3,573,269
Fair Value, Measurements, Recurring | Level 2 | Foreign corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	1,712,484	1,371,354
Fair Value, Measurements, Recurring | Level 2 | Foreign corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	3,664,098	3,509,162
Fair Value, Measurements, Recurring | Level 2 | Asset-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	1,831,879	1,421,852
Fair Value, Measurements, Recurring | Level 2 | Commercial mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	699,453	573,930
Fair Value, Measurements, Recurring | Level 2 | Residential mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	402,456	336,216
Fair Value, Measurements, Recurring | Level 3
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	868,287	612,944
Market risk benefits assets	2,340,230	1,393,237
Fixed maturities, trading	0	0
Equity securities	43,374	28,593
Short-term investments	1,209	16,945
Cash equivalents	0	0
Other invested assets	0	0
Other assets	217,613	141,041
Reinsurance recoverables	1,465	0
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	3,472,178	2,192,760
Separate account assets	4,982	4,645
TOTAL ASSETS	3,477,160	2,197,405
Market risk benefit liabilities	5,089,766	5,521,601
Policyholders’ account balances	5,513,449	3,502,096
Payables to parent and affiliates	0	0
Other liabilities	0	0
Total liabilities	10,603,215	9,023,697
Fair Value, Measurements, Recurring | Level 3 | U.S. Treasury securities and obligations of U.S. government authorities and agencies
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 3 | Obligations of U.S. states and their political subdivisions
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 3 | Foreign government bonds
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	701	724
Fair Value, Measurements, Recurring | Level 3 | U.S. corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Fair Value, Measurements, Recurring | Level 3 | U.S. corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	338,654	243,460
Fair Value, Measurements, Recurring | Level 3 | Foreign corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	6,968	6,868
Fair Value, Measurements, Recurring | Level 3 | Foreign corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	375,625	257,168
Fair Value, Measurements, Recurring | Level 3 | Asset-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	65,687	20,502
Fair Value, Measurements, Recurring | Level 3 | Commercial mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	80,652	84,222
Fair Value, Measurements, Recurring | Level 3 | Residential mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	0
Other invested assets
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investment measured at NAV per share	67,000	69,000
Separate account assets
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investment measured at NAV per share	$ 4,805,000	$ 5,262,000

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