Reinsurance (Reinsurance amounts included in the Statement of Operations and Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Premiums:
Direct	$ 459,628	$ 462,067
Assumed	33	(156)
Ceded	(367,479)	(385,255)
Net Premiums	92,182	76,656
Policy charges and fee income:
Direct	771,189	735,938
Assumed	258,770	152,600
Ceded	1,898,786	(502,047)
Net policy charges and fee income	2,928,745	386,491
Net investment income:
Direct	519,052	350,323
Assumed	330	343
Ceded	(14,062)	(1,216)
Net investment income	505,320	349,450
Asset administration fees:
Direct	82,688	80,356
Assumed	0	0
Ceded	(26,056)	(16,154)
Net asset administration fees	56,632	64,202
Other income (loss):
Direct	44,816	225,734
Assumed	325	(293)
Ceded	168,344	19,406
Net other income (loss)	213,485	244,847
Realized investment gains (losses), net:
Direct	98,442	(245,923)
Assumed	(9,167)	138,666
Ceded	19,368	(13,422)
Realized investment gains (losses), net	108,643	(120,679)
Change in value of market risk benefits, net of related hedging gain (loss):
Direct	313,886	33,120
Assumed	(466)	(6,217)
Ceded	(221,829)	(6,701)
Net change in value of market risk benefits, net of related hedging gain (loss)	91,591	20,202
Policyholders’ benefits (including change in reserves):
Direct	951,647	878,785
Assumed	287,411	317,287
Ceded	2,852,743	(1,090,890)
Net policyholders’ benefits (including change in reserves	4,091,801	105,182
Change in estimates of liability for future policy benefits:
Direct	139,586	(48,501)
Assumed	(9,510)	1,807
Ceded	(142,081)	42,292
Net change in estimates of liability for future policy benefits	(12,005)	(4,402)
Interest credited to policyholders’ account balances:
Direct	278,098	222,575
Assumed	46,148	38,506
Ceded	(99,988)	(100,859)
Net interest credited to policyholders’ account balances	224,258	160,222
Reinsurance expense allowances and general and administrative expenses, net of capitalization and amortization	(390,041)	(117,830)
Unaffiliated activity
Premiums:
Assumed	30	(166)
Ceded	(25,152)	(16,575)
Policy charges and fee income:
Assumed	272	540
Ceded	(42,012)	(23,938)
Net investment income:
Ceded	0	10,920
Asset administration fees:
Ceded	(7,316)	0
Other income (loss):
Assumed	429	(293)
Ceded	21,804	1,622
Realized investment gains (losses), net:
Assumed	(9,167)	138,666
Ceded	25,225	(14,581)
Change in value of market risk benefits, net of related hedging gain (loss):
Assumed	(466)	(6,217)
Ceded	(98,008)	(4,773)
Policyholders’ benefits (including change in reserves):
Assumed	333	91
Ceded	(146,828)	(27,702)
Change in estimates of liability for future policy benefits:
Ceded	91,873	0
Interest credited to policyholders’ account balances:
Assumed	$ 17,459	$ 7,469