Reinsurance (Balance Sheet Reinsurance Results) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 40,710,159	$ 34,682,127
Policy loans	(1,314,064)	(1,236,077)
Deferred policy acquisition costs	(1,855,698)	(1,613,922)	$ (1,376,211)	$ (1,341,093)
Deferred sales inducements	0	0
Other assets	441,543	365,219
Other liabilities	1,390,876	1,093,143
Impacts of Reinsurance
Effects of Reinsurance [Line Items]
Reinsurance recoverables	40,710,159	34,682,127
Policy loans	(142,262)	(130,502)
Deferred policy acquisition costs	(6,989,618)	(7,267,847)
Deferred sales inducements	(515,968)	(562,052)
Other assets	258,427	185,573
Policyholders’ account balances	4,934,544	5,004,112
Future policy benefits	4,209,817	3,376,048
Other liabilities	884,641	621,856
Unaffiliated
Effects of Reinsurance [Line Items]
Other assets	0	100
Other liabilities	$ 43,100	$ 27,200