Business Segments - Schedule of Reconciliation of Segment Operating Information to Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Revenue:
Premium	$ 4,890,220	$ 4,666,272	$ 4,456,017
Net investment income	1,130,198	1,135,631	1,056,884
Segment revenue	6,020,418	5,801,903	5,512,901
Realized gains (losses)	(27,788)	(24,188)	(65,676)
Other income	1,688	354	308
Total revenue	5,994,318	5,778,069	5,447,533
Expenses:
Policy obligations	2,878,485	2,873,523	2,836,212
Required interest on reserves	9,683	28,769	38,224
Amortization of acquisition costs	446,347	408,447	378,024
Commissions	347,519	318,572	295,870
Premium taxes	97,957	96,781	91,011
Non-deferred acquisition costs	202,545	186,387	172,269
Segment profit or (loss)	2,037,882	1,889,424	1,701,291
Insurance administrative expenses:
Salaries	137,015	129,369	119,699
Other employee costs	41,609	36,176	35,905
Information technology costs	82,573	80,555	64,998
Legal costs	22,510	30,478	15,335
Other administrative costs	71,888	65,852	65,224
Parent expense	14,182	12,400	10,866
Stock-based compensation expense	53,355	40,118	30,736
Interest expense	141,221	127,092	102,316
Legal proceedings	17,053	21,575	900
Other expenses	2,183	2,620	4,170
Annuity	(7,782)	(7,282)	(8,492)
Total expenses	4,558,343	4,451,432	4,253,267
Income before income taxes	1,435,975	1,326,637	1,194,266
Life
Revenue:
Premium	3,363,470	3,261,347	3,137,244
Net investment income	0	0	0
Segment revenue	3,363,470	3,261,347	3,137,244
Expenses:
Policy obligations	1,924,929	2,000,977	2,050,789
Required interest on reserves	(845,875)	(811,147)	(772,701)
Amortization of acquisition costs	386,450	356,223	327,426
Commissions	174,029	159,703	145,678
Premium taxes	68,132	68,360	64,571
Non-deferred acquisition costs	146,444	134,634	128,509
Segment profit or (loss)	1,509,361	1,352,597	1,192,972
Health
Revenue:
Premium	1,526,750	1,404,925	1,318,773
Net investment income	0	0	0
Segment revenue	1,526,750	1,404,925	1,318,773
Expenses:
Policy obligations	931,141	851,577	776,362
Required interest on reserves	(113,832)	(110,342)	(106,516)
Amortization of acquisition costs	59,897	52,224	50,598
Commissions	173,490	158,869	150,192
Premium taxes	29,825	28,421	26,440
Non-deferred acquisition costs	56,101	51,753	43,760
Segment profit or (loss)	390,128	372,423	377,937
Investment
Revenue:
Premium	0	0	0
Net investment income	1,130,198	1,135,631	1,056,884
Segment revenue	1,130,198	1,135,631	1,056,884
Expenses:
Policy obligations	22,415	20,969	9,061
Required interest on reserves	969,390	950,258	917,441
Amortization of acquisition costs	0	0	0
Commissions	0	0	0
Premium taxes	0	0	0
Non-deferred acquisition costs	0	0	0
Segment profit or (loss)	$ 138,393	$ 164,404	$ 130,382