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, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	$ 1,771,553	$ 1,550,096
Fixed maturities, trading	12,727	13,700
Equity securities	7,311	7,512
Other invested assets	107,524	89,536
Reinsurance recoverables	4,310,574	3,200,642
Receivables from parent and affiliates	39,848	32,820
Separate account assets	15,290,949	15,904,208
TOTAL ASSETS	22,181,871	21,435,345
Future policy benefits	3,425,560	2,302,959
Policyholders’ account balances	2,477,893	2,424,120
Payables to parent and affiliates	26,632	24,958
Total liabilities	21,380,081	20,799,443
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	1,742,000	761,000
Embedded Derivative, Fair Value of Embedded Derivative Gross Asset	24,000	60,000
Embedded Derivative, Fair Value of Embedded Derivative Gross Liability	1,766,000	821,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	1,771,553	1,550,096
Fixed maturities, trading	12,727	13,700
Equity securities	7,311	7,512
Cash equivalents	35,939	55,896
Other invested assets	34,248	21,384
Reinsurance recoverables	1,741,924	760,558
Receivables from parent and affiliates	2,316	2,433
Subtotal excluding separate account assets	3,606,018	2,411,579
Separate account assets	13,415,971	13,927,275
TOTAL ASSETS	17,021,989	16,338,854
Future policy benefits	1,741,924	760,558
Policyholders’ account balances	143,242	133,793
Payables to parent and affiliates	0	0
Total liabilities	1,885,166	894,351
Assets Netting	(8,466)	(13,029)
Liabilities Netting	(8,457)	(13,043)
Netting	(0)	0
Fair Value, Measurements, Recurring | Other invested assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Netting	(8,466)	(13,029)
Fair Value, Measurements, Recurring | Payables to parent and affiliates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities Netting	(8,457)	(13,043)
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	16,052	16,015
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	180,090	133,677
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	78,794	77,280
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	856,451	697,520
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	240,606	233,215
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	59,180	57,993
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	162,287	163,892
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	18,437	18,542
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	155,374	147,389
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	4,282	4,573
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	0	0
Cash equivalents	0	0
Other invested assets	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	0	0
Separate account assets	0	0
TOTAL ASSETS	0	0
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	1,751,321	1,548,918
Fixed maturities, trading	12,727	13,700
Equity securities	124	207
Cash equivalents	35,939	55,896
Other invested assets	42,714	34,413
Reinsurance recoverables	0	0
Receivables from parent and affiliates	2,316	2,433
Subtotal excluding separate account assets	1,845,141	1,655,567
Separate account assets	13,415,971	13,927,275
TOTAL ASSETS	15,261,112	15,582,842
Future policy benefits	0	0
Policyholders’ account balances	0	0
Payables to parent and affiliates	8,457	13,043
Total liabilities	8,457	13,043
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	16,052	16,015
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	180,090	133,677
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	78,794	77,280
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	856,451	697,520
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	240,303	232,903
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	59,180	57,993
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	142,358	163,026
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	18,437	18,542
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	155,374	147,389
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	4,282	4,573
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale	20,232	1,178
Fixed maturities, trading	0	0
Equity securities	7,187	7,305
Cash equivalents	0	0
Other invested assets	0	0
Reinsurance recoverables	1,741,924	760,558
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	1,769,343	769,041
Separate account assets	0	0
TOTAL ASSETS	1,769,343	769,041
Future policy benefits	1,741,924	760,558
Policyholders’ account balances	143,242	133,793
Payables to parent and affiliates	0	0
Total liabilities	1,885,166	894,351
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	0	0
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	303	312
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	0	0
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	19,929	866
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	0	0
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	2,900	3,300
Separate account assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investment measured at NAV per share	$ 1,875,000	$ 1,977,000