Fair Value of Assets and Liabilities (Level 3 by Pricing Source) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Reinsurance recoverables	$ 9,141,712	$ 4,940,011
Receivables from parent and affiliates	148,430	162,625
Total assets	127,523,847	121,349,590
Total liabilities	8,657,255	5,205,434
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	17,073	18,413
Other long-term investments	2,479	5,704
Reinsurance recoverables	9,141,712	4,940,011
Receivables from parent and affiliates	556	5,000
Total assets	9,300,919	5,237,967
Future policy benefits	8,657,255	5,205,434
Total liabilities	8,657,255	5,205,434
Level 3 | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	98,272	95,492
Level 3 | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	40,827	173,347
Level 3 | Internal
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	4,554	165
Other long-term investments	0	3,260
Reinsurance recoverables	9,141,712	4,940,011
Receivables from parent and affiliates	0	0
Total assets	9,189,624	4,984,086
Future policy benefits	8,657,255	5,205,434
Total liabilities	8,657,255	5,205,434
Level 3 | Internal | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	43,272	40,492
Level 3 | Internal | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	86	158
Level 3 | External
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	12,519	18,248
Other long-term investments	2,479	2,444
Reinsurance recoverables	0	0
Receivables from parent and affiliates	556	5,000
Total assets	111,295	253,881
Future policy benefits	0	0
Total liabilities	0	0
Level 3 | External | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	55,000	55,000
Level 3 | External | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	$ 40,741	$ 173,189