Policyholders' Liabilities (Policyholders' Account Balances) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	$ 18,894,893	$ 17,204,824
Interest-sensitive life contracts
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	14,593,376	13,344,332
Individual annuities
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	2,861,882	2,549,289
Guaranteed interest accounts
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	310,321	363,332
Other
Liability for Policyholders' Account Balances, by Product Segment [Line Items]
Total policyholders’ account balances	$ 1,129,314	$ 947,871