BUSINESS SEGMENT AND FOREIGN INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[1]	$ 4,934	$ 4,416	$ 4,461
Net investment gains (losses)	[2],[3],[4],[5],[6]	462	(229)	(15)
Other income (loss)		(74)	(28)	(1)
Earnings before income taxes		5,322	4,159	4,445
Income taxes applicable to pretax adjusted earnings		915	864	1,147
Effect of foreign currency translation on after tax adjusted earnings		(38)	31	15
Interest expense on debt		170	167	135
Aflac Japan
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[3],[5]	3,754	3,263	3,261
Hedge costs		76	206	257
Net interest cash flows from derivatives		(33)	9	(17)
Aflac U.S.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[6]	1,478	1,268	1,272
Net interest cash flows from derivatives		2	3
Corporate and other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax adjusted earnings	[2],[4],[7]	(298)	(115)	(72)
Hedge income		57	97	89
Gain (loss) on change in fair value of derivative, interest rate component		55	$ 56	$ 66
All other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (Loss) from federal historic rehabilitation and solar tax credit investments		(138)
Federal historic rehabilitation and solar tax credits, amount		$ 115

[1] Includes $170, $167 and $135 of interest expense on debt in 2021, 2020 and 2019, respectively.

[2] A gain of $55, $56 and $66 in 2021, 2020 and 2019, 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.

[3] 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.

[4] 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.

[5] 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.

[6] 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.

[7] 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.