Business Segments - Schedule of Reconciliation of Segment Operating Information to Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue:
Premium	$ 1,172,593	$ 1,119,335	$ 3,485,002	$ 3,325,345
Net investment income	284,964	266,926	853,178	785,275
Other income	42	50	192	185
Total revenue	1,457,599	1,386,311	4,338,372	4,110,805
Expenses:
Policy benefits	688,184	719,044	2,155,671	2,144,481
Required interest on reserves	0	0	0	0
Amortization of acquisition costs	104,310	95,757	305,703	282,159
Commissions, premium taxes, and non-deferred acquisition costs	149,693	138,677	447,605	414,933
Insurance administrative expense	89,195	74,585	252,718	223,951
Parent expense	6,446	3,718	15,888	9,391
Stock-based compensation expense	9,233	7,567	28,590	22,732
Interest expense	31,388	25,955	91,413	76,640
Total benefits and expenses	1,078,449	1,065,303	3,297,588	3,174,287
Subtotal	379,150	321,008	1,040,784	936,518
Non-operating items	3,966	1,137	8,368	1,137
Measure of segment profitability (pretax)	383,116	322,145	1,049,152	937,655
Realized gains (losses)	(2,192)	(2,193)	(26,580)	(78,963)
Legal proceedings	3,329		5,764	1,137
Non-operating expenses	(637)	(1,137)	(2,604)
Income before income taxes	376,958	318,815	1,014,204	857,555
Life
Revenue:
Premium	818,638	788,099	2,438,385	2,342,429
Expenses:
Amortization of acquisition costs	90,070	82,523	263,753	243,285
Health
Revenue:
Premium	353,955	331,236	1,046,617	982,916
Expenses:
Amortization of acquisition costs	13,852	12,816	40,774	37,608
Annuity
Revenue:
Premium	0	0	0	0
Operating Segments
Expenses:
Non-operating items	0	0	0	0
Operating Segments | Life
Revenue:
Premium	818,638	788,099	2,438,385	2,342,429
Net investment income	0	0	0	0
Other income	0	0	0	0
Total revenue	818,638	788,099	2,438,385	2,342,429
Expenses:
Policy benefits	454,502	515,676	1,493,165	1,536,317
Required interest on reserves	(203,875)	(194,199)	(605,397)	(575,801)
Amortization of acquisition costs	90,070	82,523	263,753	243,285
Commissions, premium taxes, and non-deferred acquisition costs	90,758	84,011	270,347	251,136
Insurance administrative expense	0	0	0	0
Parent expense	0	0	0	0
Stock-based compensation expense	0	0	0	0
Interest expense	0	0	0	0
Total benefits and expenses	431,455	488,011	1,421,868	1,454,937
Subtotal	387,183	300,088	1,016,517	887,492
Measure of segment profitability (pretax)	387,183	300,088	1,016,517	887,492
Operating Segments | Health
Revenue:
Premium	353,955	331,236	1,046,617	982,916
Net investment income	0	0	0	0
Other income	0	0	0	0
Total revenue	353,955	331,236	1,046,617	982,916
Expenses:
Policy benefits	221,926	193,790	629,676	580,676
Required interest on reserves	(27,717)	(26,732)	(82,300)	(79,603)
Amortization of acquisition costs	13,852	12,816	40,774	37,608
Commissions, premium taxes, and non-deferred acquisition costs	58,931	54,662	177,246	163,784
Insurance administrative expense	0	0	0	0
Parent expense	0	0	0	0
Stock-based compensation expense	0	0	0	0
Interest expense	0	0	0	0
Total benefits and expenses	266,992	234,536	765,396	702,465
Subtotal	86,963	96,700	281,221	280,451
Measure of segment profitability (pretax)	86,963	96,700	281,221	280,451
Operating Segments | Annuity
Revenue:
Premium	0	0	0	0
Net investment income	0	0	0	0
Other income	0	0	0	0
Total revenue	0	0	0	0
Expenses:
Policy benefits	5,716	6,854	17,786	21,502
Required interest on reserves	(7,829)	(9,353)	(24,358)	(29,327)
Amortization of acquisition costs	388	418	1,176	1,266
Commissions, premium taxes, and non-deferred acquisition costs	4	4	12	13
Insurance administrative expense	0	0	0	0
Parent expense	0	0	0	0
Stock-based compensation expense	0	0	0	0
Interest expense	0	0	0	0
Total benefits and expenses	(1,721)	(2,077)	(5,384)	(6,546)
Subtotal	1,721	2,077	5,384	6,546
Measure of segment profitability (pretax)	1,721	2,077	5,384	6,546
Operating Segments | Investment
Revenue:
Premium	0	0	0	0
Net investment income	284,964	266,926	853,178	785,275
Other income	0	0	0	0
Total revenue	284,964	266,926	853,178	785,275
Expenses:
Policy benefits	6,040	2,724	15,044	5,986
Required interest on reserves	239,421	230,284	712,055	684,731
Amortization of acquisition costs	0	0	0	0
Commissions, premium taxes, and non-deferred acquisition costs	0	0	0	0
Insurance administrative expense	0	0	0	0
Parent expense	0	0	0	0
Stock-based compensation expense	0	0	0	0
Interest expense	0	0	0	0
Total benefits and expenses	245,461	233,008	727,099	690,717
Subtotal	39,503	33,918	126,079	94,558
Measure of segment profitability (pretax)	39,503	33,918	126,079	94,558
Corporate & Other
Revenue:
Premium	0	0	0	0
Net investment income	0	0	0	0
Other income	42	50	192	185
Total revenue	42	50	192	185
Expenses:
Policy benefits	0	0	0	0
Required interest on reserves	0	0	0	0
Amortization of acquisition costs	0	0	0	0
Commissions, premium taxes, and non-deferred acquisition costs	0	0	0	0
Insurance administrative expense	88,465	74,585	251,072	223,951
Parent expense	3,210	2,581	9,166	8,254
Stock-based compensation expense	9,233	7,567	28,590	22,732
Interest expense	31,388	25,955	91,413	76,640
Total benefits and expenses	132,296	110,688	380,241	331,577
Subtotal	(132,254)	(110,638)	(380,049)	(331,392)
Non-operating items	0	0	0	0
Measure of segment profitability (pretax)	(132,254)	(110,638)	(380,049)	(331,392)
Adjustments
Revenue:
Premium	0	0	0	0
Net investment income	0	0	0	0
Other income	0	0	0	0
Total revenue	0	0	0	0
Expenses:
Policy benefits	0	0	0	0
Required interest on reserves	0	0	0	0
Amortization of acquisition costs	0	0	0	0
Commissions, premium taxes, and non-deferred acquisition costs	0	0	0	0
Insurance administrative expense	730	0	1,646	0
Parent expense	3,236	1,137	6,722	1,137
Stock-based compensation expense	0	0	0	0
Interest expense	0	0	0	0
Total benefits and expenses	3,966	1,137	8,368	1,137
Subtotal	(3,966)	(1,137)	(8,368)	(1,137)
Non-operating items	3,966	1,137	8,368	1,137
Measure of segment profitability (pretax)	$ 0	$ 0	$ 0	$ 0