Reinsurance (Reinsurance amounts included in the Statements of Operations and Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Premiums:
Direct	$ 8,054	$ 12,113
Assumed	9,095	10,181
Ceded	116	(1,260)
Net premiums	17,265	21,034
Policy charges and fee income:
Direct	121,611	145,713
Assumed	395,088	420,026
Ceded	(8,765)	(10,449)
Net policy charges and fee income	507,934	555,290
Asset administration fees and other income:
Direct	38,745	26,033
Assumed	72,695	75,892
Ceded	(2,052)	(2,388)
Net asset administration fees and other income	109,388	99,537
Realized investment gains (losses), net:
Direct	(834,208)	(748,325)
Assumed	(515,709)	1,349,104
Ceded	7,698	(42,089)
Realized investment gains (losses), net	(1,342,219)	558,690
Policyholders' benefits (including change in reserves):
Direct	7,103	18,164
Assumed	2,357	17,892
Ceded	(1,510)	(1,030)
Net policyholders' benefits (including change in reserves)	7,950	35,026
Interest credited to policyholders’ account balances:
Direct	6,010	36,388
Assumed	4,811	35,791
Ceded	(394)	(2,609)
Net interest credited to policyholders’ account balances	10,427	69,570
Reinsurance expense allowances and general and administrative expenses, net of capitalization and amortization	199,255	296,197
Unaffiliated activity
Policy charges and fee income:
Ceded	0	(200)
Policyholders' benefits (including change in reserves):
Ceded	$ (0)	$ (200)