Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	$ 39,166,072	$ 34,986,160
Market risk benefit assets	2,508,967	2,637,363	$ 2,537,000
Fixed maturities, trading	4,278,652	3,845,045
Equity securities	2,384,261	2,623,820
Other invested assets	2,040,612	1,582,094
Reinsurance recoverables and deposit receivables	49,168,211	48,247,817
Receivables from parent and affiliates	641,061	678,028
Separate account assets	113,586,513	118,143,256
TOTAL ASSETS	238,575,786	238,454,729
Market risk benefit liabilities	4,803,284	4,281,244	$ 4,388,000
Payables to parent and affiliates	4,267,511	3,653,848
Total liabilities	233,107,659	233,752,749
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	1,080,660	1,099,241
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	517,184	541,066
Foreign government securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	393,237	310,334
U.S. corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	15,560,822	13,238,428
U.S. corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	6,308,786	5,754,097
Foreign corporate public securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	4,373,302	3,698,851
Foreign corporate private securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	5,780,039	5,341,633
Asset-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	3,816,356	3,750,663
Commercial mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	981,540	895,775
Residential mortgage-backed securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	354,146	356,072
Fair Value, Measurements, Recurring
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	39,166,072	34,986,160
Market risk benefit assets	2,508,967	2,637,363
Fixed maturities, trading	4,278,652	3,845,045
Equity securities	2,384,261	2,623,820
Short-term investments	459,613	496,285
Cash equivalents	1,828,424	2,851,283
Other invested assets	80,482	24,499
Reinsurance recoverables and deposit receivables	716,745	645,193
Receivables from parent and affiliates	567,031	520,462
Subtotal excluding separate account assets	51,990,247	48,630,110
Separate account assets	106,781,195	111,699,552
TOTAL ASSETS	158,771,442	160,329,662
Market risk benefit liabilities	4,803,284	4,281,244
Policyholders’ account balances	11,817,734	12,624,585
Payables to parent and affiliates	4,218,150	3,615,277
Other liabilities	18,377	7,350
Total liabilities	20,857,545	20,528,456
Assets netting	(12,673,497)	(15,308,195)
Liabilities netting	(22,085,694)	(23,619,586)
Derivative liability, cash collateral	(9,412,000)	(8,311,000)
Fair Value, Measurements, Recurring | Payables to parent and affiliates
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities netting	(22,078,754)	(23,617,643)
Fair Value, Measurements, Recurring | Other liabilities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities netting	(6,940)	(1,943)
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	1,080,660	1,099,241
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	517,184	541,066
Fair Value, Measurements, Recurring | Foreign government securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	393,237	310,334
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	15,560,822	13,238,428
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	6,308,786	5,754,097
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	4,373,302	3,698,851
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	5,780,039	5,341,633
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	3,816,356	3,750,663
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	981,540	895,775
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	354,146	356,072
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 benefit assets	0	0
Fixed maturities, trading	0	0
Equity securities	2,342,713	2,587,791
Short-term investments	0	0
Cash equivalents	0	0
Other invested assets	12,288	2,302
Reinsurance recoverables and deposit receivables	0	0
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	2,355,001	2,590,093
Separate account assets	319,136	273,288
TOTAL ASSETS	2,674,137	2,863,381
Market risk benefit liabilities	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	0	0
Other liabilities	7,660	7,988
Total liabilities	7,660	7,988
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 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 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	36,793,550	33,086,013
Market risk benefit assets	0	0
Fixed maturities, trading	4,126,571	3,778,760
Equity securities	21,274	15,514
Short-term investments	354,852	390,745
Cash equivalents	1,828,321	2,851,250
Other invested assets	12,741,659	15,330,249
Reinsurance recoverables and deposit receivables	0	0
Receivables from parent and affiliates	187,671	169,072
Subtotal excluding separate account assets	56,053,898	55,621,603
Separate account assets	106,449,817	111,415,717
TOTAL ASSETS	162,503,715	167,037,320
Market risk benefit liabilities	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	26,296,904	27,232,920
Other liabilities	5,153	1,274
Total liabilities	26,302,057	27,234,194
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	1,080,660	1,099,241
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	517,184	541,066
Fair Value, Measurements, Recurring | Level 2 | Foreign government securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	393,237	309,686
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	15,560,822	13,238,428
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	5,307,604	4,996,400
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	4,366,433	3,692,124
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	5,346,922	4,906,450
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	2,961,274	3,126,089
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	905,268	820,457
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	354,146	356,072
Fair Value, Measurements, Recurring | Level 3
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	2,372,522	1,900,147
Market risk benefit assets	2,508,967	2,637,363
Fixed maturities, trading	152,081	66,285
Equity securities	20,274	20,515
Short-term investments	104,761	105,540
Cash equivalents	103	33
Other invested assets	32	143
Reinsurance recoverables and deposit receivables	716,745	645,193
Receivables from parent and affiliates	379,360	351,390
Subtotal excluding separate account assets	6,254,845	5,726,609
Separate account assets	12,242	10,547
TOTAL ASSETS	6,267,087	5,737,156
Market risk benefit liabilities	4,803,284	4,281,244
Policyholders’ account balances	11,817,734	12,624,585
Payables to parent and affiliates	0	0
Other liabilities	12,504	31
Total liabilities	16,633,522	16,905,860
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 securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	0	648
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	1,001,182	757,697
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	6,869	6,727
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	433,117	435,183
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	855,082	624,574
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	76,272	75,318
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	40,000	44,000
Separate account assets
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investment measured at NAV per share	$ 6,805,000	$ 6,444,000