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, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Premiums:
Direct	$ 6,581	$ 7,717	$ 12,718	$ 14,215
Assumed	6,017	8,003	16,093	18,430
Ceded	(1,321)	(707)	(1,772)	(1,053)
Net premiums	11,277	15,013	27,039	31,592
Policy charges and fee income:
Direct	108,788	95,670	216,120	201,924
Assumed	412,053	367,194	819,191	765,855
Ceded	(6,693)	(7,182)	(13,580)	(15,228)
Net policy charges and fee income	514,148	455,682	1,021,731	952,551
Asset management and service fees(2):
Direct	24,568	21,195	48,484	44,242
Assumed	83,554	72,285	165,176	149,065
Ceded	(2,072)	(1,840)	(4,089)	(3,818)
Net asset management and service fees	106,050	91,640	209,571	189,489
Realized investment gains (losses), net:
Direct	493,028	(4,643,352)	(1,613,057)	4,399,638
Assumed	(1,355,940)	1,305,763	4,021,957	(8,754,691)
Ceded	25,948	(38,175)	(116,728)	221,598
Realized investment gains (losses), net	(836,964)	(3,375,764)	2,292,172	(4,133,455)
Policyholders' benefits (including change in reserves):
Direct	7,216	467	24,505	59,633
Assumed	(9,606)	(38,289)	2,784	150,235
Ceded	(1,221)	54	(1,272)	(5,107)
Net policyholders' benefits (including change in reserves)	(3,611)	(37,768)	26,017	204,761
Interest credited to policyholders’ account balances:
Direct	14,546	(12,284)	96,167	33,555
Assumed	6,363	(22,561)	77,309	45,854
Ceded	350	1,591	(4,307)	307
Net interest credited to policyholders’ account balances	21,259	(33,254)	169,169	79,716
Reinsurance expense allowances and general and administrative expenses, net of capitalization and amortization	174,726	38,342	514,437	583,806
Unaffiliated activity
Policy charges and fee income:
Ceded	(100)	(400)	(400)	(700)
Policyholders' benefits (including change in reserves):
Ceded	$ (300)	$ (500)	$ (400)	$ (400)