BUSINESS SEGMENT AND SELECTED FOREIGN CURRENCY TRANSLATION ITEMS - Operations by Segment - Revenues (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, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		$ 3,385	$ 3,476	$ 3,573	$ 3,688	$ 3,523	$ 3,535	$ 3,764	$ 4,079	$ 14,123	[1]	$ 14,901	[1]	$ 17,095	[1]
Net investment income		865	1,004	999	943	896	920	937	903	3,811		3,656		3,818
Other income (loss)		38	47	45	46	50	50	50	69	177		220		173
Total revenues		3,777	4,950	5,172	4,800	3,948	4,704	5,315	5,173	18,701		19,140		21,554
Net investment gains (losses)		$ (511)	$ 423	$ 555	$ 123	$ (521)	$ 199	$ 564	$ 122	590		363		468
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues										17,747		18,643		21,037
Segment Reconciling Items
Segment Reporting, Revenue Reconciling Item [Line Items]
Hedge costs										157		112		76
Hedge income										(121)		(68)		(57)
Net interest cash flows from derivatives										328		90		30
Life insurance
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										1,973		2,150		2,628
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										8,047		9,186		11,301
Net investment income										3,033		2,867		3,139
Aflac Japan | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net investment income										2,582		2,669		3,031
Other income (loss)										35		35		41
Total revenues										10,664		11,890		14,373
Aflac Japan | Cancer | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance	[2]									4,054		4,702		5,718
Aflac Japan | Medical and other health | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance	[2]									2,451		2,706		3,287
Aflac Japan | Life insurance | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance	[2]									1,542		1,778		2,296
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										5,675		5,570		5,614
Net investment income										854		759		752
Aflac U.S. | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net investment income										820		755		754
Other income (loss)										128		161		121
Total revenues										6,623		6,486		6,489
Aflac U.S. | Accident | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										1,284		1,314		1,362
Aflac U.S. | Disability | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										1,249		1,171		1,162
Aflac U.S. | Critical care | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										1,743		1,753		1,797
Aflac U.S. | Hospital indemnity | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										720		722		730
Aflac U.S. | Dental/vision | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										214		199		188
Aflac U.S. | Life insurance | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										432		372		332
Aflac U.S. | Other | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										33		39		43
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance										400		145		180
Net investment income										(77)		30		(73)
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, Revenue Reconciling Item [Line Items]
Total revenues	[3]									$ 460		$ 267		$ 175

[1] Includes a gain (loss) of $20, $(42) and $(11) in 2023, 2022 and 2021, respectively, related to remeasurement of the deferred profit liability for limited-payment contracts.

[2] 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.

[3] 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.