Reinsurance (Reinsurance amounts included in the Statements of Financial Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 646,139	$ 572,102
Deferred policy acquisition costs	4,493,194	4,447,505
Deferred sales inducements	863,990	889,598
Value of business acquired	31,539	33,222
Other assets	102,493	85,310
Policyholders’ account balances	5,732,732	5,353,596
Future policy benefits	12,794,173	9,368,986
Reinsurance payables	251,804	232,937
Other liabilities	403,368	811,016
Impacts of Reinsurance
Effects of Reinsurance [Line Items]
Reinsurance recoverables	646,139	572,102
Deferred policy acquisition costs	3,778,155	3,703,166
Deferred sales inducements	473,085	476,608
Value of business acquired	(2,399)	(2,431)
Other assets	90,297	79,992
Policyholders’ account balances	3,185,754	3,098,537
Future policy benefits	8,247,032	5,680,939
Reinsurance payables	251,804	232,937
Other liabilities	291,469	290,330
Unaffiliated activity
Effects of Reinsurance [Line Items]
Reinsurance recoverables	100	0
Reinsurance payables	$ 100	$ 100