Reinsurance (Reinsurance amounts included in the Statements of Operations and Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Premiums:
Direct	$ 7,717	$ 8,381	$ 14,215	$ 16,435
Assumed	8,003	10,398	18,430	19,493
Ceded	(707)	(308)	(1,053)	(192)
Net premiums	15,013	18,471	31,592	35,736
Policy charges and fee income:
Direct	95,670	122,420	201,924	244,031
Assumed	367,194	411,058	765,855	806,146
Ceded	(7,182)	(8,690)	(15,228)	(17,455)
Net policy charges and fee income	455,682	524,788	952,551	1,032,722
Asset administration fees and other income:
Direct	35,964	41,226	105,837	79,971
Assumed	71,725	76,079	148,964	148,774
Ceded	(1,840)	(2,100)	(3,819)	(4,152)
Net asset administration fees and other income	105,849	115,205	250,982	224,593
Realized investment gains (losses), net:
Direct	(4,643,352)	593,738	4,399,638	(240,470)
Assumed	1,305,763	(1,530,524)	(8,754,691)	(2,046,233)
Ceded	(38,175)	42,571	221,598	50,269
Realized investment gains (losses), net	(3,375,764)	(894,215)	(4,133,455)	(2,236,434)
Policyholders' benefits (including change in reserves):
Direct	467	17,616	59,633	24,719
Assumed	(38,289)	31,619	150,235	33,976
Ceded	54	(1,345)	(5,107)	(2,855)
Net policyholders' benefits (including change in reserves)	(37,768)	47,890	204,761	55,840
Interest credited to policyholders’ account balances:
Direct	(12,284)	15,335	33,555	21,345
Assumed	(22,561)	19,283	45,854	24,094
Ceded	1,591	(1,263)	307	(1,657)
Net interest credited to policyholders’ account balances	(33,254)	33,355	79,716	43,782
Reinsurance expense allowances and general and administrative expenses, net of capitalization and amortization	38,342	240,225	583,806	439,480
Unaffiliated activity
Policy charges and fee income:
Ceded	(400)	(1,000)	(700)	(1,000)
Policyholders' benefits (including change in reserves):
Ceded	$ (500)	$ (100)	$ (400)	$ (100)