BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) $ in Millions		3 Months Ended
		Mar. 31, 2022 USD ($) segment	Mar. 31, 2021 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of reportable insurance business segments | segment		2
Net earned premiums		$ 4,178	$ 4,593
Total adjusted revenues		5,126	5,552
Net investment gains (losses)	[1],[2],[3],[4]	146	317
Total revenues		5,272	5,869
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		2,724	3,123
Adjusted net investment income	[1],[3]	680	705
Other income		9	13
Total adjusted revenues		3,413	3,841
Hedge costs		26	19
Net interest cash flows from derivatives		(10)	(8)
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,413	1,422
Adjusted net investment income	[4]	184	176
Other income		42	30
Total adjusted revenues		1,639	1,628
Net interest cash flows from derivatives		1
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Total adjusted revenues	[2],[5]	74	83
Hedge income		11	$ 17
Income (loss) from federal historic rehabilitation and solar tax credit investments		(12)
Federal historic rehabilitation and solar tax credits, amount		$ 16

[1] Amortized hedge costs of $26 and $19 for the three-month periods ended March 31, 2022, and 2021, 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 $11 and $17 for the three-month periods ended March 31, 2022, and 2021, 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 $(10) and $(8) for the three-month periods ended March 31, 2022 and 2021, 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 $1 the three-month period ended March 31, 2022, 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 $12 for the three-month period ended March 31, 2022, is included as a reduction to net investment income. Tax credits on these investments of $16 for the three-month period ended March 31, 2022, have 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.