Fair Value of Assets and Liabilities (Balances of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	$ 6,840,932	$ 6,194,564
Trading account assets, at fair value	64,612	49,661
Equity securities, available-for-sale	51,973	29,500
Separate account assets	109,350,121	109,194,192
Margin Deposit Assets	198,000	156,000
Embedded Derivative Cumulative Decrease	5,205,000	4,994,000
Embedded Derivative Gross Asset	655,000	577,000
Embedded Derivative Gross Liability	5,860,000	5,571,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	6,840,932	6,194,564
Trading account assets, at fair value	64,612	49,661
Equity securities, available-for-sale	51,973	29,500
Short-term investments	54,806	121,272
Cash equivalents	194,925	67,843
Other long-term investments	73,873	29,572
Reinsurance recoverables	4,940,011	4,897,545
Receivables from parent and affiliates	162,625	177,672
Sub-total excluding separate account assets	12,383,757	11,567,629
Separate account assets	109,350,121	109,194,192
Total assets	121,733,878	120,761,821
Future policy benefits	5,205,434	4,993,611
Payables to parent and affiliates	0	0
Total liabilities	5,205,434	4,993,611
Asset, Netting	(230,554)	(215,066)
Liability, Netting	(32,849)	(58,687)
Fair Value, Measurements, Recurring | Other long-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset, Netting	(230,554)	(215,066)
Fair Value, Measurements, Recurring | Payables to parent and affiliates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability, Netting	(32,849)	(58,687)
U.S. Treasury securities and obligations of U.S. government authorities and agencies | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	94,049	92,082
Obligations of U.S. states and their political subdivisions | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	624,769	325,654
Foreign government bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	70,410	38,498
All other U.S. public corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	2,690,554	2,655,102
All other U.S. private corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	1,344,929	1,253,545
All other foreign public corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	275,349	206,848
All other foreign private corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	778,642	581,663
Corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets, at fair value	44,374	42,131
Asset-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	435,131	402,251
Trading account assets, at fair value	1,990	1,990
Commercial mortgage-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	404,345	498,879
Residential mortgage-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	122,754	140,042
Equity securities, available-for-sale | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets, at fair value	18,248	5,540
Level 1 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Trading account assets, at fair value	0	0
Equity securities, available-for-sale	39	107
Short-term investments	18,713	6,997
Cash equivalents	50,998	41,584
Other long-term investments	0	0
Reinsurance recoverables	0	$ 0
Receivables from parent and affiliates	0
Sub-total excluding separate account assets	69,750	$ 48,688
Separate account assets	0	0
Total assets	69,750	48,688
Future policy benefits	0	0
Payables to parent and affiliates	0	0
Total liabilities	0	0
Level 1 | U.S. Treasury securities and obligations of U.S. government authorities and agencies | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | Obligations of U.S. states and their political subdivisions | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | Foreign government bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | All other U.S. public corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | All other U.S. private corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | All other foreign public corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | All other foreign private corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | Corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets, at fair value	0	0
Level 1 | Asset-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Trading account assets, at fair value	0	0
Level 1 | Commercial mortgage-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | Residential mortgage-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 1 | Equity securities, available-for-sale | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets, at fair value	0	0
Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	6,572,093	6,009,546
Trading account assets, at fair value	46,364	44,121
Equity securities, available-for-sale	51,769	28,643
Short-term investments	36,093	114,275
Cash equivalents	143,927	26,259
Other long-term investments	297,394	242,523
Reinsurance recoverables	0	0
Receivables from parent and affiliates	157,625	158,469
Sub-total excluding separate account assets	7,305,265	6,623,836
Separate account assets	108,967,162	108,891,268
Total assets	116,272,427	115,515,104
Future policy benefits	0	0
Payables to parent and affiliates	32,849	58,687
Total liabilities	32,849	58,687
Level 2 | U.S. Treasury securities and obligations of U.S. government authorities and agencies | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	94,049	92,082
Level 2 | Obligations of U.S. states and their political subdivisions | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	624,769	325,654
Level 2 | Foreign government bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	70,410	38,498
Level 2 | All other U.S. public corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	2,635,551	2,594,010
Level 2 | All other U.S. private corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	1,322,213	1,239,006
Level 2 | All other foreign public corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	275,349	206,848
Level 2 | All other foreign private corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	760,869	572,493
Level 2 | Corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets, at fair value	44,374	42,131
Level 2 | Asset-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	261,784	302,034
Trading account assets, at fair value	1,990	1,990
Level 2 | Commercial mortgage-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	404,345	498,879
Level 2 | Residential mortgage-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	122,754	140,042
Level 2 | Equity securities, available-for-sale | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets, at fair value	0	0
Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	268,839	185,018
Trading account assets, at fair value	18,248	5,540
Equity securities, available-for-sale	165	750
Short-term investments	0	0
Cash equivalents	0	0
Other long-term investments	7,033	2,115
Reinsurance recoverables	4,940,011	4,897,545
Receivables from parent and affiliates	5,000	19,203
Sub-total excluding separate account assets	5,239,296	5,110,171
Separate account assets	382,959	302,924
Total assets	5,622,255	5,413,095
Future policy benefits	5,205,434	4,993,611
Payables to parent and affiliates	0	0
Total liabilities	5,205,434	4,993,611
Level 3 | U.S. Treasury securities and obligations of U.S. government authorities and agencies | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 3 | Obligations of U.S. states and their political subdivisions | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 3 | Foreign government bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 3 | All other U.S. public corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	55,003	61,092
Level 3 | All other U.S. private corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	22,716	14,539
Level 3 | All other foreign public corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 3 | All other foreign private corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	17,773	9,170
Level 3 | Corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets, at fair value	0	0
Level 3 | Asset-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	173,347	100,217
Trading account assets, at fair value	0	0
Level 3 | Commercial mortgage-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 3 | Residential mortgage-backed securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, available-for-sale:	0	0
Level 3 | Equity securities, available-for-sale | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account assets, at fair value	$ 18,248	$ 5,540