Business Segments - Assets by Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and invested assets	$ 19,827,199				$ 18,300,927
Accrued investment income	270,396				259,581
Deferred acquisition costs	6,009,477				5,535,697				$ 5,067,539	$ 4,587,547
Goodwill	481,791				481,791
Other assets	1,462,636				1,408,801
Total assets	28,051,499	$ 26,223,345	$ 26,769,793	$ 26,922,329	25,986,797	$ 25,248,899	$ 26,424,294	$ 28,215,723
Corporate & Other
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and invested assets	0				0
Accrued investment income	0				0
Deferred acquisition costs	0				0
Goodwill	0				0
Other assets	1,462,636				1,408,801
Total assets	1,462,636				1,408,801
Life
Segment Reporting, Asset Reconciling Item [Line Items]
Deferred acquisition costs	5,271,775				4,844,291				4,412,015	3,983,021	$ 3,983,021
Life | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and invested assets	0				0
Accrued investment income	0				0
Deferred acquisition costs	5,271,775				4,844,291
Goodwill	309,609				309,609
Other assets	0				0
Total assets	5,581,384				5,153,900
Health
Segment Reporting, Asset Reconciling Item [Line Items]
Deferred acquisition costs	734,735				686,763				649,082	596,217	$ 612,718
Health | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and invested assets	0				0
Accrued investment income	0				0
Deferred acquisition costs	734,735				686,763
Goodwill	172,182				172,182
Other assets	0				0
Total assets	906,917				858,945
Annuity
Segment Reporting, Asset Reconciling Item [Line Items]
Deferred acquisition costs	2,967				4,643				$ 6,442	$ 8,309
Annuity | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and invested assets	0				0
Accrued investment income	0				0
Deferred acquisition costs	2,967				4,643
Goodwill	0
Other assets	0				0
Total assets	2,967				4,643
Investment | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and invested assets	19,827,199				18,300,927
Accrued investment income	270,396				259,581
Deferred acquisition costs	0				0
Goodwill	0				0
Other assets	0				0
Total assets	$ 20,097,595				$ 18,560,508