Fair Value of Assets and Liabilities (Level 3 by Pricing Source) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Separate account assets	$ 106,289,140	$ 109,194,192
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other long-term investments	27,951	29,572
Reinsurance recoverables	5,388,800	4,897,545
Receivables from parent and affiliates	175,332	177,672
Subtotal excluding separate account assets	12,717,871	11,567,629
Separate account assets	106,289,140	109,194,192
Total assets	119,007,011	120,761,821
Future policy benefits	5,661,265	4,993,611
Total liabilities	5,661,265	4,993,611
Level 3 | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	18,422	6,290
Other long-term investments	2,169	2,115
Reinsurance recoverables	5,388,800	4,897,545
Receivables from parent and affiliates	3,030	19,203
Subtotal excluding separate account assets	5,656,049	5,110,171
Separate account assets	361,589	302,924
Total assets	6,017,638	5,413,095
Future policy benefits	5,661,265	4,993,611
Total liabilities	5,661,265	4,993,611
Level 3 | Fair Value, Measurements, Recurring | Separate account assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Separate account assets	361,589	302,924
Level 3 | Fair Value, Measurements, Recurring | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable Securities, Fixed Maturities	88,347	84,801
Level 3 | Fair Value, Measurements, Recurring | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable Securities, Fixed Maturities	155,281	100,217
Level 3 | Fair Value, Measurements, Recurring | Internal
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	174	750
Other long-term investments	731	565
Reinsurance recoverables	5,388,800	4,897,545
Receivables from parent and affiliates	0	0
Subtotal excluding separate account assets	5,421,567	4,922,836
Total assets	5,509,064	5,006,947
Future policy benefits	5,661,265	4,993,611
Total liabilities	5,661,265	4,993,611
Level 3 | Fair Value, Measurements, Recurring | Internal | Separate account assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Separate account assets	87,497	84,111
Level 3 | Fair Value, Measurements, Recurring | Internal | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable Securities, Fixed Maturities	31,669	23,712
Level 3 | Fair Value, Measurements, Recurring | Internal | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable Securities, Fixed Maturities	193	264
Level 3 | Fair Value, Measurements, Recurring | External
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	18,248	5,540
Other long-term investments	1,438	1,550
Reinsurance recoverables	0	0
Receivables from parent and affiliates	3,030	19,203
Subtotal excluding separate account assets	234,482	187,335
Total assets	508,574	406,148
Future policy benefits	0	0
Total liabilities	0	0
Level 3 | Fair Value, Measurements, Recurring | External | Separate account assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Separate account assets	274,092	218,813
Level 3 | Fair Value, Measurements, Recurring | External | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable Securities, Fixed Maturities	56,678	61,089
Level 3 | Fair Value, Measurements, Recurring | External | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable Securities, Fixed Maturities	$ 155,088	$ 99,953