BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		$ 3,456	$ 3,688
Net investment income		1,000	943
Other income		29	46
Total revenues		5,436	4,800
Net investment gains (losses)		951	123
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		4,419	4,579
Segment Reconciling Items
Segment Reporting, Revenue Reconciling Item [Line Items]
Amortized hedge costs		6	58
Amortized hedge income		(28)	(29)
Net interest (income) expense from from derivatives associated with certain investment strategies		88	69
Aflac Japan | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,816	2,170
Net investment income		648	611
Other income		9	9
Total revenues		2,473	2,790
Aflac U.S. | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,475	1,428
Net investment income		206	197
Other income		18	35
Total revenues		1,699	1,660
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Change in value of federal historic rehabilitation and solar tax credit investments		(32)	(51)
Federal historic rehabilitation and solar tax credits, amount		33	52
Corporate and other | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	[1]	$ 247	$ 129

[1] The change in value of federal historic rehabilitation and solar investments in partnerships of $32 and $51 for the three-month periods ended March 31, 2024, and 2023, respectively, is included as a reduction to net investment income. Tax credits on these investments of $33 and $52 for the three-month periods ended March 31, 2024, and 2023, respectively, have been recorded as an income tax benefit in the consolidated statements of earnings. See Note 3 for additional information on these investments.