Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	$ 26,131,780	$ 19,025,401
Market risk benefits assets	2,367,243	1,393,237	[1]
Fixed maturities, trading	2,796,446	1,936,159
Equity securities	844,950	143,072
Short-term investments	380,366
Other invested assets	1,222,985	1,088,613
Other Assets	2,078,938	1,331,427	[1]
Reinsurance recoverables	38,709,651	37,096,562
Receivables from parent and affiliates	332,583	224,921
Separate account assets	119,188,485	114,051,246
TOTAL ASSETS	213,309,041	193,473,118
Market risk benefit liabilities	5,144,401	5,521,601	[1]
Payables to parent and affiliates	2,667,696	2,126,571
Total liabilities	208,787,616	188,436,923
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	975,287	281,792
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	776,627	628,200
Foreign government bonds
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	281,986	273,462
U.S. corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	9,495,912	6,443,944
U.S. corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	4,989,494	3,816,729
Foreign corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	1,706,094	1,378,222
Foreign corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	4,630,982	3,766,330
Asset-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	2,027,550	1,442,354
Commercial mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	851,778	658,152
Residential mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	396,070	336,216
Equity securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investment measured at NAV per share	14,600
Fair Value, Measurements, Recurring
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	26,131,780	19,025,401
Market risk benefits assets	2,367,243	1,393,237
Fixed maturities, trading	2,796,446	1,936,159
Equity securities	830,340	143,072
Short-term investments	313,866	98,160
Cash equivalents	1,644,125	1,432,182
Other invested assets	17,718	47,111
Other Assets	224,019	141,041
Reinsurance recoverables	69,745
Receivables from parent and affiliates	147,984	148,075
Subtotal excluding separate account assets	34,543,266	24,364,438
Separate account assets	113,929,793	108,789,313
TOTAL ASSETS	148,473,059	133,153,751
Market risk benefit liabilities	5,144,401	5,521,601
Policyholders’ account balances	7,689,929	3,502,096
Payables to parent and affiliates	2,651,123	2,084,917
Other liabilities	6,340	(9,267)
Total liabilities	15,491,793	11,099,347
Assets netting	(9,028,019)	(7,637,939)
Liabilities netting	(18,596,679)	(16,568,912)
Netting	(9,569,000)	(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	(9,028,019)	(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	(18,588,647)	(16,568,242)
Fair Value, Measurements, Recurring | Other liabilities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities netting	(8,032)	(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	975,287	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	776,627	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	281,986	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	9,495,912	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	4,989,494	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	1,706,094	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	4,630,982	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	2,027,550	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	851,778	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	396,070	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	790,346	108,076
Short-term investments	31,879	0
Cash equivalents	447,396	0
Other invested assets	23,432	4,223
Other Assets	0	0
Reinsurance recoverables	0
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	1,293,053	112,299
Separate account assets	176,239	102,243
TOTAL ASSETS	1,469,292	214,542
Market risk benefit liabilities	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	0	0
Other liabilities	8,032	899
Total liabilities	8,032	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	24,939,518	18,412,457
Market risk benefits assets	0	0
Fixed maturities, trading	2,762,398	1,936,159
Equity securities	11,285	6,403
Short-term investments	280,228	81,215
Cash equivalents	1,196,729	1,432,182
Other invested assets	9,022,304	7,680,827
Other Assets	0	0
Reinsurance recoverables	0
Receivables from parent and affiliates	147,984	148,075
Subtotal excluding separate account assets	38,360,446	29,697,318
Separate account assets	113,747,569	108,682,425
TOTAL ASSETS	152,108,015	138,379,743
Market risk benefit liabilities	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	21,239,770	18,653,159
Other liabilities	6,340	(9,496)
Total liabilities	21,246,110	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	975,287	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	776,627	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	281,304	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	9,495,912	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	4,476,258	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	1,698,965	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	4,137,004	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	1,928,428	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	773,663	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	396,070	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	1,192,262	612,944
Market risk benefits assets	2,367,243	1,393,237
Fixed maturities, trading	34,048	0
Equity securities	28,709	28,593
Short-term investments	1,759	16,945
Cash equivalents	0	0
Other invested assets	1	0
Other Assets	224,019	141,041
Reinsurance recoverables	69,745
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	3,917,786	2,192,760
Separate account assets	5,985	4,645
TOTAL ASSETS	3,923,771	2,197,405
Market risk benefit liabilities	5,144,401	5,521,601
Policyholders’ account balances	7,689,929	3,502,096
Payables to parent and affiliates	0	0
Other liabilities	0	0
Total liabilities	12,834,330	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	682	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	513,236	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	7,129	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	493,978	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	99,122	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	78,115	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	$ 5,259,000	$ 5,262,000

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