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, 2023	Dec. 31, 2022
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale		$ 21,576,351	$ 19,025,401
Market Risk Benefit, Asset		1,427,488	1,393,237
Fixed maturities, trading		2,262,905	1,936,159
Equity securities		201,065	143,072
Other invested assets		1,075,216	1,088,613
Other assets	[1]	1,500,270	1,331,427
Reinsurance recoverables	[1]	37,853,981	37,096,562
Receivables from parent and affiliates		254,512	224,921
Separate account assets		117,293,384	114,051,246
TOTAL ASSETS		200,979,254	193,473,118
Market risk benefit liabilities		5,621,681	5,521,601
Payables to parent and affiliates		1,773,307	2,126,571
Other liabilities	[1]	4,123,022	3,597,373
Total liabilities		194,839,806	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		21,576,351	19,025,401
Market Risk Benefit, Asset		1,427,488	1,393,237
Fixed maturities, trading		2,262,905	1,936,159
Equity securities		201,065	143,072
Short-term investments		231,360	98,160
Cash equivalents		1,493,898	1,432,182
Other invested assets		11,232	47,111
Other assets		155,763	141,041
Reinsurance recoverables		1,357	0
Receivables from parent and affiliates		148,996	148,075
Subtotal excluding separate account assets		27,510,415	24,364,438
Separate account assets		111,839,749	108,789,313
TOTAL ASSETS		139,350,164	133,153,751
Market risk benefit liabilities		5,621,681	5,521,601
Policyholders’ account balances		4,129,043	3,502,096
Payables to parent and affiliates		1,736,768	2,084,917
Other liabilities		9,806	(9,267)
Total liabilities		11,497,298	11,099,347
Assets netting		(6,654,487)	(7,637,939)
Liabilities netting		(16,132,600)	(16,568,912)
Netting		(9,478,000)	(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		(6,654,487)	(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		(16,127,517)	(16,568,242)
Fair Value, Measurements, Recurring | Other liabilities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities netting		(5,083)	(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		334,378	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		652,515	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		284,148	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		8,080,417	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		3,969,677	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		1,573,373	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		3,891,512	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		1,598,275	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		781,272	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		410,784	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 Benefit, Asset		0	0
Fixed maturities, trading		0	0
Equity securities		146,680	108,076
Short-term investments		0	0
Cash equivalents		47,900	0
Other invested assets		6,658	4,223
Other assets		0	0
Reinsurance recoverables		0	0
Receivables from parent and affiliates		0	0
Subtotal excluding separate account assets		201,238	112,299
Separate account assets		102,362	102,243
TOTAL ASSETS		303,600	214,542
Market risk benefit liabilities		0	0
Policyholders’ account balances		0	0
Payables to parent and affiliates		0	0
Other liabilities		26,409	899
Total liabilities		26,409	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		20,810,875	18,412,457
Market Risk Benefit, Asset		0	0
Fixed maturities, trading		2,256,655	1,936,159
Equity securities		11,211	6,403
Short-term investments		216,944	81,215
Cash equivalents		1,445,998	1,432,182
Other invested assets		6,659,061	7,680,827
Other assets		0	0
Reinsurance recoverables		0	0
Receivables from parent and affiliates		148,996	148,075
Subtotal excluding separate account assets		31,549,740	29,697,318
Separate account assets		111,732,834	108,682,425
TOTAL ASSETS		143,282,574	138,379,743
Market risk benefit liabilities		0	0
Policyholders’ account balances		0	0
Payables to parent and affiliates		17,864,285	18,653,159
Other liabilities		(11,520)	(9,496)
Total liabilities		17,852,765	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		334,378	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		652,515	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		283,434	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		8,080,417	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		3,725,930	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		1,566,216	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		3,606,523	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		1,497,087	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		653,591	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		410,784	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		765,476	612,944
Market Risk Benefit, Asset		1,427,488	1,393,237
Fixed maturities, trading		6,250	0
Equity securities		43,174	28,593
Short-term investments		14,416	16,945
Cash equivalents		0	0
Other invested assets		0	0
Other assets		155,763	141,041
Reinsurance recoverables		1,357	0
Receivables from parent and affiliates		0	0
Subtotal excluding separate account assets		2,413,924	2,192,760
Separate account assets		4,553	4,645
TOTAL ASSETS		2,418,477	2,197,405
Market risk benefit liabilities		5,621,681	5,521,601
Policyholders’ account balances		4,129,043	3,502,096
Payables to parent and affiliates		0	0
Other liabilities		0	0
Total liabilities		9,750,724	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		714	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		243,747	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		7,157	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		284,989	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		101,188	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		127,681	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		68,000	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		$ 5,454,000	$ 5,262,000

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