Reinsurance (Amounts included in the Statement of Financial Position) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 534,694	$ 588,608
Deferred policy acquisition costs	4,559,234	4,344,361
Deferred sales inducements	1,027,819	978,823
Value of business acquired	(35,187)	(30,287)
Other assets	121,330	169,649
Policyholders’ account balances	4,744,406	4,736,889
Future policy benefits	8,971,369	8,686,196
Reinsurance payables	234,859	275,822
Other liabilities	489,532	489,007
Impacts of Reinsurance
Effects of Reinsurance [Line Items]
Reinsurance recoverables	534,694	588,608
Deferred policy acquisition costs	3,722,540	3,557,248
Deferred sales inducements	542,311	520,182
Value of business acquired	(2,732)	(2,357)
Other assets	104,074	112,802
Policyholders’ account balances	2,738,620	2,576,357
Future policy benefits	5,352,110	5,130,753
Reinsurance payables	234,859	275,822
Other liabilities	332,821	335,713
Unaffiliated activity
Effects of Reinsurance [Line Items]
Reinsurance payables	$ 100	$ 100