BUSINESS SEGMENT INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues		$ 3,398	$ 5,436
Benefits and claims, excluding reserve remeasurement		1,986	2,066
Reserve remeasurement (gains) losses		(41)	(56)
Total benefits and claims, net		1,945	2,010
Amortization of deferred policy acquisition costs		216	215	$ 851
Insurance commissions		240	255
Insurance and other expenses		802	739
Total benefits and expenses		3,253	3,266
Net investment gains (losses)		(963)	951
Earnings before income taxes		145	2,170
Income taxes applicable to pretax adjusted earnings		217	202
Effect of foreign currency translation on after-tax adjusted earnings		(8)	(44)
Remeasurement gain (loss), deferred profit liability for limited-payment contracts		0	(3)
Change in value of federal historic rehabilitation and solar tax credit investments		(8)	(32)
Federal historic rehabilitation and solar tax credits, amount		7	33
Operating Segments
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues		4,319	4,419
Total benefits and expenses		3,196	3,256
Pretax adjusted earnings		1,123	1,163
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Other income (loss)		(53)	(2)
Net investment gains (losses)		(963)	951
Amortized hedge costs		7	6
Amortized hedge income		(30)	(28)
Net interest (income) expense from derivatives associated with certain investment strategies		65	88
Impact of interest from derivatives associated with notes payable		(4)	(8)
Aflac Japan | Operating Segments
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues	[1]	2,272	2,473
Benefits and claims, excluding reserve remeasurement		1,130	1,243
Reserve remeasurement (gains) losses		(25)	(26)
Total benefits and claims, net		1,105	1,217
Amortization of deferred policy acquisition costs		79	83
Insurance commissions		105	114
Insurance and other expenses		261	249
Total benefits and expenses		1,550	1,663
Pretax adjusted earnings	[1]	722	810
Aflac U.S. | Operating Segments
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues		1,721	1,699
Benefits and claims, excluding reserve remeasurement		731	715
Reserve remeasurement (gains) losses		(15)	(29)
Total benefits and claims, net		716	686
Amortization of deferred policy acquisition costs		137	132
Insurance commissions		135	141
Insurance and other expenses		375	384
Total benefits and expenses		1,363	1,343
Pretax adjusted earnings		358	356
Corporate and other | Operating Segments
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues	[2]	326	247
Total benefits and expenses		283	250
Pretax adjusted earnings	[2]	$ 43	$ (3)

[1] Includes a gain (loss) of an immaterial amount and $(3) for the three-month periods ended March 31, 2025 and 2024, respectively, related to remeasurement of the deferred profit liability for limited-payment contracts.

[2] The change in value of federal historic rehabilitation and solar investments in partnerships of $8 and $32 for the three-month periods ended March 31, 2025 and 2024, respectively, is included as a reduction to net investment income. Tax credits on these investments of $7 and $33 for the three-month periods ended March 31, 2025 and 2024, respectively, have been recorded as an income tax benefit in the consolidated statements of earnings. See Note 3 for additional information on these investments.