Reinsurance (Amounts included in the Statement of Financial Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 520,111	$ 563,428
Deferred policy acquisition costs	4,502,165	4,596,565
Deferred sales inducements	951,447	1,020,786
Value of business acquired	(35,938)	(35,109)
Other assets	108,594	121,086
Policyholders’ account balances	4,964,987	4,846,152
Future policy benefits	7,194,626	9,132,569
Reinsurance payables	247,971	262,588
Other liabilities	417,835	422,636
Impacts of Reinsurance
Effects of Reinsurance [Line Items]
Reinsurance recoverables	520,111	563,428
Deferred policy acquisition costs	3,730,602	3,766,066
Deferred sales inducements	510,603	540,389
Value of business acquired	(2,637)	(2,702)
Other assets	94,406	105,167
Policyholders’ account balances	2,965,892	2,825,030
Future policy benefits	4,144,754	5,511,496
Reinsurance payables	247,971	262,588
Other liabilities	307,582	329,019
Unaffiliated activity
Effects of Reinsurance [Line Items]
Reinsurance recoverables	0	300
Reinsurance payables	$ 100	$ 100