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, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	$ 7,339,233	$ 7,012,631
Fixed maturities, trading	81,361	82,482
Equity securities	48,931	108,457
Other invested assets	620,592	520,955
Reinsurance recoverables	42,955,806	48,367,096
Receivables from parent and affiliates	280,424	266,473
Separate account assets	150,164,599	145,740,422
TOTAL ASSETS	207,908,267	208,308,100
Future policy benefits	27,399,889	32,889,181
Payables to parent and affiliates	175,902	75,990
Other Liabilities	1,760,014	1,694,492
Total liabilities	203,829,140	204,260,384
Future policy benefits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net Liability	9,264,000	13,228,000
Embedded Derivative, Fair Value of Embedded Derivative Gross Asset	636,000	483,000
Embedded Derivative, Fair Value of Embedded Derivative Gross Liability	9,900,000	13,711,000
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	7,339,233	7,012,631
Fixed maturities, trading	81,361	82,482
Equity securities	48,931	108,457
Short-term Investments	0	49,997
Cash equivalents	202,805	397,326
Other invested assets	103,151	18,147
Reinsurance recoverables	9,275,523	13,239,539
Receivables from parent and affiliates	110,607	111,970
Subtotal excluding separate account assets	17,161,611	21,020,549
Separate account assets	144,736,239	140,583,009
TOTAL ASSETS	161,897,850	161,603,558
Future policy benefits	9,263,516	13,227,814
Policyholders’ account balances	1,156,610	1,155,274
Payables to parent and affiliates	0	0
Total liabilities	10,420,126	14,383,088
Asset Netting	(217,249)	(379,399)
Liability Netting	(229,080)	(265,826)
Netting	11,800	(113,600)
Fair Value, Measurements, Recurring | Other invested assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset Netting	(217,249)	(379,399)
Fair Value, Measurements, Recurring | Payables to parent and affiliates
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liability Netting	(229,080)	(265,826)
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	79,571	77,855
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	517,006	517,951
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	288,833	250,855
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	3,242,940	2,929,434
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	970,986	1,012,056
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	477,960	320,730
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	1,047,116	1,091,930
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	233,336	237,638
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	459,111	520,947
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	22,374	53,235
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
Fixed maturities, trading	0	0
Equity securities	133	100,268
Short-term Investments	0	49,997
Cash equivalents	115,996	49,996
Other invested assets	175	198
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	116,304	200,459
Separate account assets	61,180	0
TOTAL ASSETS	177,484	200,459
Future policy benefits	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	0	0
Total liabilities	0	0
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	7,086,068	6,780,627
Fixed maturities, trading	80,560	81,727
Equity securities	40,793	300
Short-term Investments	0	0
Cash equivalents	86,809	347,330
Other invested assets	320,225	397,348
Reinsurance recoverables	0	0
Receivables from parent and affiliates	110,607	111,970
Subtotal excluding separate account assets	7,725,062	7,719,302
Separate account assets	144,675,059	140,583,009
TOTAL ASSETS	152,400,121	148,302,311
Future policy benefits	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	229,080	265,826
Total liabilities	229,080	265,826
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	24,571	22,855
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	517,006	517,951
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	288,677	250,692
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	3,242,940	2,929,431
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	937,412	977,423
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	468,902	311,407
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	918,918	961,113
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	206,157	235,573
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	459,111	520,947
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	22,374	53,235
Fair Value, Measurements, Recurring | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	253,165	232,004
Fixed maturities, trading	801	755
Equity securities	8,005	7,889
Short-term Investments	0	0
Cash equivalents	0	0
Other invested assets	0	0
Reinsurance recoverables	9,275,523	13,239,539
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	9,537,494	13,480,187
Separate account assets	0	0
TOTAL ASSETS	9,537,494	13,480,187
Future policy benefits	9,263,516	13,227,814
Policyholders’ account balances	1,156,610	1,155,274
Payables to parent and affiliates	0	0
Total liabilities	10,420,126	14,383,088
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	55,000	55,000
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	156	163
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	3
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	33,574	34,633
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	9,058	9,323
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	128,198	130,817
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	27,179	2,065
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	0	0
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	78,000	77,000
Separate Account Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value investment measured at NAV per share	$ 5,428,000	$ 5,157,000