SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -Schedule of Impact from Adoption to AOCI and Retained Earnings (Detail) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Total transition impact, net of income taxes		$ (21,985)	$ (20,140)	$ (17,031)		$ (33,559)
Retained earnings
Total transition impact, net of income taxes		(47,993)	(44,367)	(40,963)		(37,984)
Accumulated other comprehensive income (loss)
Total transition impact, net of income taxes		$ 5,520	$ 6,429	$ 8,411		(8,934)
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12
Total transition impact, net of income taxes					$ 18,894	18,894
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings
Transition impact before income taxes					410
Less: income taxes					86
Total transition impact, net of income taxes					324	324
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Corporate and other
Transition impact before income taxes					0
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Cancer | Aflac Japan
Transition impact before income taxes					0
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Medical and other health | Aflac Japan
Transition impact before income taxes					1
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Life insurance | Aflac Japan
Transition impact before income taxes					0
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Life insurance | Aflac U.S.
Transition impact before income taxes					5
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Other | Aflac Japan
Transition impact before income taxes	[1]				398
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Other | Aflac U.S.
Transition impact before income taxes					2
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Accident | Aflac U.S.
Transition impact before income taxes					0
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Disability | Aflac U.S.
Transition impact before income taxes					0
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Critical care | Aflac U.S.
Transition impact before income taxes					4
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Hospital indemnity | Aflac U.S.
Transition impact before income taxes					0
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Retained earnings | Dental/vision | Aflac U.S.
Transition impact before income taxes					0
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss)
Transition impact before income taxes					23,507
Less: income taxes					4,937
Total transition impact, net of income taxes					18,570	$ 18,570
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Corporate and other
Transition impact before income taxes					(305)
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Cancer | Aflac Japan
Transition impact before income taxes					14,529
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Medical and other health | Aflac Japan
Transition impact before income taxes					2,382
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Life insurance | Aflac Japan
Transition impact before income taxes					3,314
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Life insurance | Aflac U.S.
Transition impact before income taxes					149
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Other | Aflac Japan
Transition impact before income taxes	[1]				433
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Other | Aflac U.S.
Transition impact before income taxes					218
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Accident | Aflac U.S.
Transition impact before income taxes					92
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Disability | Aflac U.S.
Transition impact before income taxes					149
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Critical care | Aflac U.S.
Transition impact before income taxes					2,258
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Hospital indemnity | Aflac U.S.
Transition impact before income taxes					223
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2018-12 | Accumulated other comprehensive income (loss) | Dental/vision | Aflac U.S.
Transition impact before income taxes					$ 65

[1] Impact to retained earnings is driven primarily by capping the Transition Date NPR on Care products.