Reinsurance (Reinsurance amounts included in the Statements of Financial Position) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 710,596	$ 572,102
Deferred policy acquisition costs	4,459,791	4,447,505
Deferred sales inducements	836,342	889,598
Value of business acquired	30,647	33,222
Other assets	88,211	85,310
Policyholders’ account balances	6,031,569	5,353,596
Future policy benefits	16,193,345	9,368,986
Reinsurance payables	227,948	232,937
Other liabilities	645,867	811,016
Impacts of Reinsurance
Effects of Reinsurance [Line Items]
Reinsurance recoverables	710,596	572,102
Deferred policy acquisition costs	3,719,370	3,703,166
Deferred sales inducements	448,274	476,608
Value of business acquired	(2,306)	(2,431)
Other assets	72,061	79,992
Policyholders’ account balances	3,238,585	3,098,537
Future policy benefits	10,787,006	5,680,939
Reinsurance payables	227,948	232,937
Other liabilities	284,581	290,330
Unaffiliated activity
Effects of Reinsurance [Line Items]
Reinsurance recoverables	100	0
Reinsurance payables	$ 100	$ 100