Fair Value of Assets and Liabilities (Level 3 by Pricing Source) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other long-term investments	$ 15,755	$ 72,544
Reinsurance recoverables	6,741,737	4,940,011
Receivables from parent and affiliates	161,965	162,625
Total assets	124,622,927	121,349,590
Future policy benefits	7,098,647	5,205,434
Total liabilities	7,098,647	5,205,434
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	22,349	18,413
Other long-term investments	2,444	5,704
Reinsurance recoverables	6,741,737	4,940,011
Receivables from parent and affiliates	569	5,000
Total assets	6,989,939	5,237,967
Future policy benefits	7,098,647	5,205,434
Total liabilities	7,098,647	5,205,434
Level 3 | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	98,449	95,492
Level 3 | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	124,391	173,347
Level 3 | Internal
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	4,589	165
Other long-term investments	0	3,260
Reinsurance recoverables	6,741,737	4,940,011
Receivables from parent and affiliates	0	0
Total assets	6,789,911	4,984,086
Future policy benefits	7,098,647	5,205,434
Total liabilities	7,098,647	5,205,434
Level 3 | Internal | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	43,449	40,492
Level 3 | Internal | Asset-backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	136	158
Level 3 | External
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	17,760	18,248
Other long-term investments	2,444	2,444
Reinsurance recoverables	0	0
Receivables from parent and affiliates	569	5,000
Total assets	200,028	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	$ 124,255	$ 173,189