BUSINESS SEGMENT INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[1]	$ 1,143	$ 1,306
Net investment gains (losses)	[2],[3],[4],[5],[6]	134	304
Other income (loss)		(1)	(7)
Earnings before income taxes		1,276	1,603
Income taxes applicable to pretax adjusted earnings		216	248
Effect of foreign currency translation on after tax adjusted earnings		(37)	13
Interest expense on debt		41	45
Aflac Japan
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[2],[5]	862	887
Hedge costs		26	19
Net interest cash flows from derivatives		(10)	(8)
Aflac U.S.
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[6]	325	445
Net interest cash flows from derivatives		1
Corporate and other
Segment Reporting, Reconciling Item for Adjusted Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[3],[4],[7]	(44)	(26)
Hedge income		11	17
Gain (loss) on change in fair value of derivative, interest rate component		13	$ 14
Income (loss) from federal historic rehabilitation and solar tax credit investments		(12)
Federal historic rehabilitation and solar tax credits, amount		$ 16

[1] Includes $41 and $45 for the three-month periods ended March 31, 2022, and 2021, respectively, of interest expense on debt.

[2] 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.

[3] A gain of $13 and $14 for the three-month periods ended March 31, 2022, and 2021, respectively, related to the interest rate component of the change in fair value of foreign currency swaps on notes payable has been reclassified from net investment gains (losses) and included in adjusted earnings when analyzing operations.

[4] 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 in net investment income when analyzing operations.

[5] 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.

[6] Net interest cash flows from derivatives associated with certain investment strategies of $1 for 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.

[7] 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.