Reinsurance (Reinsurance amounts included in the Statements of Operations and Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Premiums:
Direct	$ 6,498	$ 8,054
Assumed	10,427	9,095
Ceded	(346)	116
Net premiums	16,579	17,265
Policy charges and fee income:
Direct	106,254	121,611
Assumed	398,661	395,088
Ceded	(8,046)	(8,765)
Net policy charges and fee income	496,869	507,934
Asset administration fees and other income:
Direct	69,873	38,745
Assumed	77,239	72,695
Ceded	(1,979)	(2,052)
Net asset administration fees and other income	145,133	109,388
Realized investment gains (losses), net:
Direct	9,042,990	(834,208)
Assumed	(10,060,454)	(515,709)
Ceded	259,773	7,698
Realized investment gains (losses), net	(757,691)	(1,342,219)
Policyholders' benefits (including change in reserves):
Direct	59,166	7,103
Assumed	188,524	2,357
Ceded	(5,161)	(1,510)
Net policyholders' benefits (including change in reserves)	242,529	7,950
Interest credited to policyholders’ account balances:
Direct	45,839	6,010
Assumed	68,415	4,811
Ceded	(1,284)	(394)
Net interest credited to policyholders’ account balances	112,970	10,427
Reinsurance expense allowances and general and administrative expenses, net of capitalization and amortization	545,464	199,255
Unaffiliated activity
Policy charges and fee income:
Ceded	(300)	400
Policyholders' benefits (including change in reserves):
Ceded	$ 100	$ (0)