Fair Value of Assets and Liabilities (Level 3 by Pricing Source) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	$ 344,463	$ 379,237
Receivables from parent and affiliates	213,952	228,253
Future policy benefits		15,198,755
Policyholders’ account balances		17,204,824
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	77,865	72,544
Reinsurance recoverables	5,474,263	4,940,011
Receivables from parent and affiliates	137,637	162,625
Total assets	127,444,585	121,349,590
Future policy benefits	5,041,007	5,205,434
Policyholders’ account balances	20,337	0
Total liabilities	5,061,344	5,205,434
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	15,845	18,413
Other long-term investments	0	5,704
Reinsurance recoverables	5,474,263	4,940,011
Receivables from parent and affiliates	6,493	5,000
Total assets	5,619,013	5,237,967
Future policy benefits	5,041,007	5,205,434
Policyholders’ account balances	20,337	0
Total liabilities	5,061,344	5,205,434
Fair Value, Measurements, Recurring | Level 3 | Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities	102,556	95,492
Fair Value, Measurements, Recurring | Level 3 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities	19,856	173,347
Fair Value, Measurements, Recurring | Level 3 | Internal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	3,014	165
Other long-term investments	0	3,260
Reinsurance recoverables	5,474,263	4,940,011
Receivables from parent and affiliates	0	0
Total assets	5,523,047	4,984,086
Future policy benefits	5,041,007	5,205,434
Policyholders’ account balances	20,337	0
Total liabilities	5,061,344	5,205,434
Fair Value, Measurements, Recurring | Level 3 | Internal | Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities	45,715	40,492
Fair Value, Measurements, Recurring | Level 3 | Internal | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities	55	158
Fair Value, Measurements, Recurring | Level 3 | External
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	12,831	18,248
Other long-term investments	0	2,444
Reinsurance recoverables	0	0
Receivables from parent and affiliates	6,493	5,000
Total assets	95,966	253,881
Future policy benefits	0	0
Policyholders’ account balances	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | External | Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities	56,841	55,000
Fair Value, Measurements, Recurring | Level 3 | External | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities	$ 19,801	$ 173,189