Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	$ 5,631,416	$ 6,840,932
Equity securities, available-for-sale	20,102	51,973
Short-term investments	41,658	54,806
Other long-term investments	327,010	379,237
Receivables from parent and affiliates	246,811	228,253
Separate account assets	116,827,710	109,350,121
Future policy benefits	20,096,101	15,198,755
Policyholders’ account balances	18,011,323	17,204,824
Netting	(100)	198,000
Embedded Derivative, Fair Value of Embedded Derivative, Net Liability	8,480,000	5,205,000
Embedded Derivative, Fair Value of Embedded Derivative Gross Asset	996,000	655,000
Embedded Derivative, Fair Value of Embedded Derivative Gross Liability	9,476,000	5,860,000
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	5,631,416	6,840,932
Trading accounts assets	38,410	64,612
Equity securities, available-for-sale	20,102	51,973
Short-term investments	41,658	54,806
Cash equivalents	20,834	194,925
Other long-term investments	70,628	72,544
Reinsurance recoverables	9,011,140	4,940,011
Receivables from parent and affiliates	148,267	162,625
Subtotal excluding separate account assets	14,982,455	12,382,428
Separate account assets	116,334,339	108,967,162
Total assets	131,316,794	121,349,590
Future policy benefits	8,480,030	5,205,434
Policyholders’ account balances	17,159
Payables to parent and affiliates	0	0
Total liabilities	8,497,189	5,205,434
Asset Netting	(14,711)	(230,554)
Liability Netting	(14,847)	(32,849)
Fair Value, Measurements, Recurring | Other long-term investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset Netting	(14,711)	(230,554)
Fair Value, Measurements, Recurring | Payables to parent and affiliates
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liability Netting	(14,847)	(32,849)
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:	146,376	94,049
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:	598,405	624,769
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:	111,480	70,410
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:	2,436,733	2,690,554
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:	877,544	1,344,929
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:	217,003	275,349
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:	624,280	778,642
Fair Value, Measurements, Recurring | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account assets, debt	20,142	44,374
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:	194,047	435,131
Trading account assets, debt	302	1,990
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:	338,105	404,345
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:	87,443	122,754
Fair Value, Measurements, Recurring | Equity securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities, equity	17,966	18,248
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
Trading accounts assets	0	0
Equity securities, available-for-sale	37	39
Short-term investments	36,658	18,713
Cash equivalents	8,836	50,998
Other long-term investments	0	0
Reinsurance recoverables	0	0
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	45,531	69,750
Separate account assets	0	0
Total assets	45,531	69,750
Future policy benefits	0	0
Policyholders’ account balances	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 | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account assets, debt	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
Trading account assets, debt	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 1 | Equity securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities, equity	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:	5,485,909	6,572,093
Trading accounts assets	20,444	46,364
Equity securities, available-for-sale	19,944	51,769
Short-term investments	5,000	36,093
Cash equivalents	11,998	143,927
Other long-term investments	82,860	297,394
Reinsurance recoverables	0	0
Receivables from parent and affiliates	147,707	157,625
Subtotal excluding separate account assets	5,773,862	7,305,265
Separate account assets	116,334,339	108,967,162
Total assets	122,108,201	116,272,427
Future policy benefits	0	0
Policyholders’ account balances	0
Payables to parent and affiliates	14,847	32,849
Total liabilities	14,847	32,849
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:	146,376	94,049
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:	598,405	624,769
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:	111,480	70,410
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:	2,379,123	2,635,551
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:	843,949	1,322,213
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:	217,003	275,349
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:	608,025	760,869
Fair Value, Measurements, Recurring | Level 2 | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account assets, debt	20,142	44,374
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:	156,000	261,784
Trading account assets, debt	302	1,990
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:	338,105	404,345
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:	87,443	122,754
Fair Value, Measurements, Recurring | Level 2 | Equity securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities, equity	0	0
Fair Value, Measurements, Recurring | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	145,507	268,839
Trading accounts assets	17,966	18,248
Equity securities, available-for-sale	121	165
Short-term investments	0	0
Cash equivalents	0	0
Other long-term investments	2,479	5,704
Reinsurance recoverables	9,011,140	4,940,011
Receivables from parent and affiliates	560	5,000
Subtotal excluding separate account assets	9,177,773	5,237,967
Separate account assets	0	0
Total assets	9,177,773	5,237,967
Future policy benefits	8,480,030	5,205,434
Policyholders’ account balances	17,159
Payables to parent and affiliates	0	0
Total liabilities	8,497,189	5,205,434
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:	57,610	55,003
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:	33,595	22,716
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:	16,255	17,773
Fair Value, Measurements, Recurring | Level 3 | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account assets, debt	0	0
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:	38,047	173,347
Trading account assets, debt	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
Fair Value, Measurements, Recurring | Level 3 | Equity securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities, equity	$ 17,966	$ 18,248