BUSINESS SEGMENT AND FOREIGN INFORMATION - Operations by Segment - Revenues (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		$ 17,647	$ 18,622	$ 18,780
Total revenues		22,106	22,147	22,307
Total adjusted revenues		21,589	22,320	22,256
Net investment gains (losses)	[1],[2],[3],[4]	517	(173)	51
Life insurance
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		2,956	3,253	3,445
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		11,853	12,670	12,772
Adjusted net investment income	[1],[3]	3,031	2,659	2,496
Other income (loss)		41	42	45
Total revenues		14,925	15,371	15,313
Hedge costs		76	206	257
Net interest cash flows from derivatives		(33)	9	(17)
Aflac Japan | Cancer
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		5,829	6,119	6,031
Aflac Japan | Medical and other health
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		3,400	3,596	3,582
Aflac Japan | Life insurance
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		2,624	2,955	3,159
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		5,614	5,758	5,808
Adjusted net investment income	[4]	754	705	720
Other income (loss)		121	102	22
Total revenues		6,489	6,565	6,550
Net interest cash flows from derivatives		2	3
Aflac U.S. | Cancer
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		1,216	1,275	1,309
Aflac U.S. | Life insurance
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		332	298	286
Aflac U.S. | Accident and disability
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		2,524	2,614	2,665
Aflac U.S. | Other health
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		1,542	1,571	1,548
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	[2],[5]	175	384	393
Hedge income		57	97	89
All other
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums, principally supplemental health insurance		180	$ 194	$ 200
Income (Loss) from federal historic rehabilitation and solar tax credit investments		(138)
Federal historic rehabilitation and solar tax credits, amount		$ 115

[1] Amortized hedge costs of $76, $206 and $257 in 2021, 2020 and 2019, respectively, related to certain foreign currency exposure management strategies have been reclassified from net investment gains (losses) and reported as a deduction from net investment income when analyzing operations.

[2] Amortized hedge income of $57, $97 and $89 in 2021, 2020 and 2019, respectively, related to certain foreign currency exposure management strategies has been reclassified from net investment gains (losses) and reported as an increase to net investment income when analyzing operations.

[3] Net interest cash flows from derivatives associated with certain investment strategies of $(33), $9, and $(17) in 2021, 2020, and 2019, respectively, have been reclassified from net investment gains (losses) and included in adjusted earnings as a component of net investment income when analyzing operations.

[4] Net interest cash flows from derivatives associated with certain investment strategies of $2 and $3 in 2021 and 2020, respectively, have been reclassified from net investment gains (losses) and included in adjusted earnings as a component of net investment income when analyzing operations.

[5] The change in value of federal historic rehabilitation and solar investments in partnerships of $138 in 2021 is included as a reduction to net investment income. Tax credits on these investments of $115 in 2021 has been recorded as an income tax benefit in the consolidated statement of earnings. See Note 3 of the Notes to the Consolidated Financial Statements for additional information on these investments.