Reinsurance (Reinsurance amounts included in the Statement of Operations and Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Premiums:
Direct	$ 475,017	$ 468,900	$ 1,435,080	$ 1,408,157
Assumed	45	51	140	157
Ceded	(450,755)	(466,593)	(1,373,498)	(1,379,545)
Net premiums	24,307	2,358	61,722	28,769
Policy charges and fee income:
Direct	882,373	896,151	2,600,632	2,856,071
Assumed	131,877	130,113	395,960	385,820
Ceded	(863,170)	(915,635)	(2,544,508)	(2,843,402)
Net policy charges and fee income	151,080	110,629	452,084	398,489
Net investment income:
Direct	95,266	96,424	261,304	297,931
Assumed	390	427	1,184	1,230
Ceded	(1,664)	(1,595)	(5,453)	(5,093)
Net investment income	93,992	95,256	257,035	294,068
Asset administration fees:
Direct	91,953	90,797	265,612	262,616
Assumed	0	0	0	0
Ceded	(86,989)	(86,661)	(251,958)	(250,862)
Net asset administration fees	4,964	4,136	13,654	11,754
Other income:
Direct	28,529	19,631	49,817	59,459
Assumed	(112)	438	(141)	(1,033)
Ceded	3	(7)	128	(69)
Amortization of reinsurance income	1,162	1,180	3,506	(1,160)
Net other income	29,582	21,242	53,310	57,197
Realized investment gains (losses), net:
Direct	2,646,206	(2,500,567)	(7,254,543)	(4,920,019)
Assumed	0	0	0	0
Ceded	(2,647,753)	2,540,151	7,262,660	4,858,718
Realized investment gains (losses), net	(1,547)	39,584	8,117	(61,301)
Policyholders’ benefits (including change in reserves):
Direct	879,729	874,424	2,691,447	2,671,720
Assumed	196,502	252,424	766,272	747,135
Ceded	(1,020,403)	(1,080,958)	(3,229,715)	(3,287,196)
Net policyholders’ benefits (including change in reserves)	55,828	45,890	228,004	131,659
Interest credited to policyholders’ account balances:
Direct	148,411	163,479	420,163	376,590
Assumed	33,974	35,575	102,230	100,744
Ceded	(130,119)	(119,647)	(348,664)	(303,020)
Net interest credited to policyholders’ account balances	52,266	79,407	173,729	174,314
Reinsurance expense allowances and general and administrative expenses, net of capitalization and amortization	(448,254)	(475,041)	(1,330,501)	(1,393,034)
Unaffiliated activity
Premiums:
Assumed	0	100	200	200
Ceded	(2,400)	(100)	(7,500)	(300)
Policy charges and fee income:
Ceded	(18,000)	(13,000)	(39,000)	(25,000)
Other income:
Assumed	100	1,000	100	(1,000)
Realized investment gains (losses), net:
Ceded	(68,000)	61,000	160,000	117,000
Policyholders’ benefits (including change in reserves):
Assumed	100	1,000	700	1,000
Ceded	$ (20,000)	$ (8,000)	$ (44,000)	$ (12,000)