Reinsurance (Income Statement Reinsurance Results) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Premiums:
Direct	$ 1,923,708	$ 1,882,584	$ 1,807,809
Assumed	184	206	230
Ceded	(1,831,716)	(1,854,246)	(1,757,231)
Net premiums	92,176	28,544	50,808
Policy charges and fee income:
Direct	3,491,735	3,725,113	3,248,574
Assumed	587,466	519,265	497,751
Ceded	(3,454,881)	(3,700,222)	(3,212,998)
Net policy charges and fee income	624,320	544,156	533,327
Net investment income:
Direct	372,822	398,762	330,058
Assumed	1,579	1,631	1,581
Ceded	(7,051)	(6,596)	(6,352)
Net investment income	367,350	393,797	325,287
Asset administration fees:
Direct	360,438	355,118	346,727
Assumed	0	0	0
Ceded	(341,300)	(339,062)	(332,359)
Net asset administration fees	19,138	16,056	14,368
Other income:
Direct	78,445	83,891	68,931
Assumed	(1)	(293)	96
Ceded	165	(59)	(55)
Amortization of reinsurance income	4,647	21	3,992
Net other income	83,256	83,560	72,964
Realized investment gains (losses), net:
Direct	(3,593,799)	(1,912,241)	769,114
Assumed	0	0	0
Ceded	3,530,823	1,795,492	(936,392)
Realized investment gains (losses), net	(62,976)	(116,749)	(167,278)
Policyholders’ benefits (including change in reserves):
Direct	3,584,011	3,352,159	2,647,574
Assumed	1,055,277	885,542	599,589
Ceded	(4,341,139)	(4,084,627)	(3,097,664)
Net policyholders’ benefits (including change in reserves)	298,149	153,074	149,499
Interest credited to policyholders’ account balances:
Direct	536,886	470,551	499,458
Assumed	136,153	135,355	141,307
Ceded	(439,664)	(418,677)	(468,772)
Net interest credited to policyholders’ account balances	233,375	187,229	171,993
Net reinsurance expense allowances, net of capitalization and amortization	(1,589,113)	(1,772,111)	(1,587,360)
Unaffiliated
Premiums:
Assumed	200	200	200
Ceded	(10,500)	(600)	(200)
Policy charges and fee income:
Ceded	(54,000)	(34,000)	(20,000)
Other income:
Assumed	0	(300)	100
Realized investment gains (losses), net:
Ceded	73,000	44,000	(34,000)
Policyholders’ benefits (including change in reserves):
Assumed	900	1,900	0
Ceded	$ (70,000)	$ (30,000)	$ (10,000)