Segment Information - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Operating revenues	$ 3,103.0	$ 4,089.0	$ 11,464.0	$ 7,981.0
Revenue adjustments from annuity and life insurance product features	177.0	196.0	562.0	589.0
Credit loss-related adjustments	(38.0)	(88.0)	(91.0)	(123.0)
Investment gains (losses)	14.0	(57.0)	(30.0)	(317.0)
Changes in the fair value of reinsurance-related embedded derivatives, trading securities and certain mortgage loans	(232.0)	(416.0)	(464.0)	(326.0)
GLB rider fees ceded to LNBAR	(235.0)	(242.0)	(704.0)	(703.0)
Gains (losses) on other non-financial assets -sale of subsidiaries/businesses, pre-tax		0.0		481.0
Total revenues	2,789.0	3,482.0	10,737.0	7,582.0
Other Operations
Segment Reporting Information [Line Items]
Operating revenues	58.0	55.0	135.0	114.0
Revenue adjustments from annuity and life insurance product features	0.0	0.0	0.0	0.0
Credit loss-related adjustments	(28.0)	(21.0)	(48.0)	(32.0)
Investment gains (losses)	(18.0)	(30.0)	(76.0)	(214.0)
Changes in the fair value of reinsurance-related embedded derivatives, trading securities and certain mortgage loans	(6.0)	1.0	(23.0)	2.0
GLB rider fees ceded to LNBAR	0.0	0.0	0.0	0.0
Gains (losses) on other non-financial assets -sale of subsidiaries/businesses, pre-tax		0.0		481.0
Total revenues	6.0	5.0	(12.0)	351.0
Annuities | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	1,142.0	1,101.0	3,390.0	3,421.0
Revenue adjustments from annuity and life insurance product features	211.0	332.0	643.0	879.0
Credit loss-related adjustments	10.0	(44.0)	(10.0)	(66.0)
Investment gains (losses)	(1.0)	(43.0)	6.0	(45.0)
Changes in the fair value of reinsurance-related embedded derivatives, trading securities and certain mortgage loans	(112.0)	(249.0)	(233.0)	(183.0)
GLB rider fees ceded to LNBAR	(235.0)	(242.0)	(703.0)	(702.0)
Gains (losses) on other non-financial assets -sale of subsidiaries/businesses, pre-tax		0.0		0.0
Total revenues	1,015.0	855.0	3,093.0	3,304.0
Life Insurance | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	1,247.0	1,249.0	3,676.0	3,748.0
Revenue adjustments from annuity and life insurance product features	(34.0)	(136.0)	(81.0)	(290.0)
Credit loss-related adjustments	(17.0)	(7.0)	(18.0)	4.0
Investment gains (losses)	34.0	22.0	46.0	21.0
Changes in the fair value of reinsurance-related embedded derivatives, trading securities and certain mortgage loans	(83.0)	(40.0)	(126.0)	(17.0)
GLB rider fees ceded to LNBAR	0.0	0.0	0.0	0.0
Gains (losses) on other non-financial assets -sale of subsidiaries/businesses, pre-tax		0.0		0.0
Total revenues	1,147.0	1,088.0	3,497.0	3,466.0
Group Protection | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	318.0	1,353.0	3,274.0	(273.0)
Revenue adjustments from annuity and life insurance product features	0.0	0.0	0.0	0.0
Credit loss-related adjustments	(2.0)	(2.0)	(5.0)	(2.0)
Investment gains (losses)	(1.0)	(1.0)	0.0	(8.0)
Changes in the fair value of reinsurance-related embedded derivatives, trading securities and certain mortgage loans	(31.0)	(128.0)	(82.0)	(128.0)
GLB rider fees ceded to LNBAR	0.0	0.0	0.0	0.0
Gains (losses) on other non-financial assets -sale of subsidiaries/businesses, pre-tax		0.0		0.0
Total revenues	284.0	1,222.0	3,187.0	(411.0)
Retirement Plan Services | Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	338.0	331.0	989.0	971.0
Revenue adjustments from annuity and life insurance product features	0.0	0.0	0.0	0.0
Credit loss-related adjustments	(1.0)	(14.0)	(10.0)	(27.0)
Investment gains (losses)	0.0	(5.0)	(6.0)	(71.0)
Changes in the fair value of reinsurance-related embedded derivatives, trading securities and certain mortgage loans	0.0	0.0	0.0	0.0
GLB rider fees ceded to LNBAR	0.0	0.0	(1.0)	(1.0)
Gains (losses) on other non-financial assets -sale of subsidiaries/businesses, pre-tax		0.0		0.0
Total revenues	$ 337.0	$ 312.0	$ 972.0	$ 872.0