Reinsurance (Reinsurance amounts included in the Statements of Financial Position) (Details) - USD ($) $ in Thousands	Mar. 31, 2020		Dec. 31, 2019
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 944,229		$ 621,510
Deferred policy acquisition costs	4,095,019	[1]	4,455,683
Deferred sales inducements	699,396		812,724
Value of business acquired	28,282		30,025
Other assets	213,171		139,933
Policyholders’ account balances	6,596,004		6,180,359
Future policy benefits	26,612,760		12,932,461
Reinsurance payables	285,038		235,318
Other liabilities	881,363	[1]	447,405
Impacts of Reinsurance
Effects of Reinsurance [Line Items]
Reinsurance recoverables	944,229		621,510
Deferred policy acquisition costs	3,420,946		3,725,719
Deferred sales inducements	371,872		437,594
Value of business acquired	(2,106)		(2,275)
Other assets	59,559		65,819
Policyholders’ account balances	3,328,104		3,253,474
Future policy benefits	18,800,396		8,328,777
Reinsurance payables	285,038		235,318
Other liabilities	383,016		337,909
Unaffiliated activity
Effects of Reinsurance [Line Items]
Reinsurance recoverables	100		200
Other assets	(7,900)		(3,900)
Reinsurance payables	100		100
Other liabilities	$ 115,400		$ 60,400

[1] March 31, 2020 amounts include the impacts of the January 1, 2020 adoption of ASU 2016-13. See Note 2 for details.