Schedule II - Aflac Incorporated (Parent Only) - Condensed Statement of Earnings (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Income Statements, [Line Items]
Management and service fees from subsidiaries		$ 38	$ 47	$ 45	$ 46	$ 50	$ 50	$ 50	$ 69	$ 177	$ 220	$ 173
Net investment income		865	1,004	999	943	896	920	937	903	3,811	3,656	3,818
Net investment gains (losses)		(511)	423	555	123	(521)	199	564	122	590	363	468
Total revenues		3,777	4,950	5,172	4,800	3,948	4,704	5,315	5,173	18,701	19,140	21,554
Interest expense										195	226	238
Total acquisition and operating expenses										5,228	5,384	5,870
Income tax expense (benefit)		$ 21	$ 236	$ 191	$ 154	$ 342	$ (452)	$ 314	$ 247	603	451	977
Net earnings										4,659	4,418	4,231
Expense on extinguishment of debt												48
Parent Company
Condensed Income Statements, [Line Items]
Management and service fees from subsidiaries	[1]									151	136	130
Net investment income										(174)	3	(93)
Interest from subsidiaries	[1]									1	2	2
Net investment gains (losses)										301	(228)	206
Total revenues										279	(87)	245
Interest expense										187	215	222
Other operating expenses	[2]									295	275	300
Total acquisition and operating expenses										482	490	522
Earnings before income taxes and equity in earnings of subsidiaries										(203)	(577)	(277)
Income tax expense (benefit)										(444)	(208)	(144)
Earnings before equity in earnings of subsidiaries										241	(369)	(133)
Equity in earnings of subsidiaries	[1]									4,418	4,787	4,364
Net earnings										$ 4,659	$ 4,418	4,231
Expense on extinguishment of debt												$ 48

[1] Eliminated in consolidation

[2] Includes expense of $48 in 2021 for the early extinguishment of debt