Revenue from Contracts with Customers - Summary of Disaggregation of Revenues from Contracts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	$ 803,375	$ 688,385	$ 1,546,204	$ 1,378,422
Term Life Insurance Segment [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	426,944	411,873	867,357	832,943
Term Life Insurance Segment [Member] | Total Segment Revenues from Contracts with Customers [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	12,624	12,280	25,274	24,513
Term Life Insurance Segment [Member] | Total Segment Revenues from Contracts with Customers [Member] | Other, Net [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	12,624	12,280	25,274	24,513
Term Life Insurance Segment [Member] | Revenues from Sources Other Than Contracts with Customers (Segregated Funds) [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	414,320	399,593	842,083	808,430
Investment and Savings Product Segment [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	260,906	214,509	504,622	424,711
Investment and Savings Product Segment [Member] | Total Segment Revenues from Contracts with Customers [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	247,552	200,695	477,435	397,097
Investment and Savings Product Segment [Member] | Total Segment Revenues from Contracts with Customers [Member] | Other, Net [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	3,224	3,121	6,482	6,240
Investment and Savings Product Segment [Member] | Total Segment Revenues from Contracts with Customers [Member] | Commissions and Fees [Member] | Sales-based Revenues [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	101,177	74,958	189,924	147,346
Investment and Savings Product Segment [Member] | Total Segment Revenues from Contracts with Customers [Member] | Commissions and Fees [Member] | Asset-based Revenues [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	119,411	99,521	234,110	197,625
Investment and Savings Product Segment [Member] | Total Segment Revenues from Contracts with Customers [Member] | Commissions and Fees [Member] | Account-based Revenues [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	23,740	23,095	46,919	45,886
Investment and Savings Product Segment [Member] | Revenues from Sources Other Than Contracts with Customers (Segregated Funds) [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	13,354	13,814	27,187	27,614
Senior Health Segment [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	12,420	14,890	19,300	33,599
Senior Health Segment [Member] | Total Segment Revenues from Contracts with Customers [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	12,420	14,890	19,300	33,599
Senior Health Segment [Member] | Total Segment Revenues from Contracts with Customers [Member] | Other, Net [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	844	3,519	1,648	6,474
Senior Health Segment [Member] | Total Segment Revenues from Contracts with Customers [Member] | Commissions and Fees [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	11,576	11,371	17,652	27,125
Corporate and Other Distributed Products Segment Revenues [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	103,105	47,113	154,925	87,169
Corporate and Other Distributed Products Segment Revenues [Member] | Total Segment Revenues from Contracts with Customers [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	11,275	11,606	20,465	21,517
Corporate and Other Distributed Products Segment Revenues [Member] | Total Segment Revenues from Contracts with Customers [Member] | Other, Net [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	764	1,235	1,467	2,436
Corporate and Other Distributed Products Segment Revenues [Member] | Total Segment Revenues from Contracts with Customers [Member] | Commissions and Fees [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	10,511	10,371	18,998	19,081
Corporate and Other Distributed Products Segment Revenues [Member] | Revenues from Sources Other Than Contracts with Customers (Segregated Funds) [Member]
Disaggregation Of Revenue [Line Items]
Disaggregation of revenues from contracts with customers	$ 91,830	$ 35,507	$ 134,460	$ 65,652