BUSINESS SEGMENT AND SELECTED FOREIGN CURRENCY TRANSLATION ITEMS - Operations by Segment - Pretax Earnings (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		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, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other income (loss)										$ 39	$ 0	$ (73)
Net investment gains (losses)		$ (511)	$ 423	$ 555	$ 123	$ (521)	$ 199	$ 564	$ 122	590	363	468
Earnings before income taxes		$ 289	$ 1,805	$ 1,825	$ 1,342	$ 538	$ 1,329	$ 1,708	$ 1,294	5,262	4,869	5,208
Income taxes applicable to pretax adjusted earnings										577	808	893
Effect of foreign currency translation on after tax adjusted earnings										(113)	(262)	(35)
Interest expense on debt										190	217	225
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings										4,310	4,422	4,819
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Hedge costs										157	112	76
Net interest cash flows from derivatives										328	90	30
Hedge income										(121)	(68)	(57)
Gain (loss) on change in fair value of derivative, interest rate component										(41)	(50)	(55)
Aflac Japan | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[1]									3,234	3,281	3,756
Aflac U.S. | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings										1,501	1,359	1,356
Corporate and other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Change in value of federal historic rehabilitation and solar tax credit investments										(343)	(91)	(138)
Federal historic rehabilitation and solar tax credits, amount										334	83	115
Corporate and other | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[2]									$ (425)	$ (218)	$ (293)

[1] Includes a gain (loss) of $20, $(42) and $(11) for 2023, 2022 and 2021, 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 $343, $91 and $138 in 2023, 2022 and 2021, respectively, is included as a reduction to net investment income. Tax credits on these investments of $334, $83 and $115 in 2023, 2022 and 2021, respectively, have been recorded as an income tax benefit in the consolidated statements of earnings. See Note 3 for additional information on these investments.