Schedule II - Aflac Incorporated (Parent Only) - Condensed Statement of Earnings (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Income Statements, [Line Items]
Net investment income		$ 3,818	$ 3,638	$ 3,578
Net investment gains (losses)		468	(270)	(135)
Total revenues		22,106	22,147	22,307
Interest expense		238	242	228
Total acquisition and operating expenses		6,208	6,192	5,920
Income tax expense (benefit)		997	(619)	1,141
Net earnings		4,325	4,778	3,304
Parent Company
Condensed Income Statements, [Line Items]
Management and service fees from subsidiaries	[1]	130	131	151
Net investment income		(93)	62	77
Interest from subsidiaries	[1]	2	3	4
Net investment gains (losses)		206	399	98
Total revenues		245	595	330
Interest expense		222	221	200
Other operating expenses	[2]	300	277	221
Total acquisition and operating expenses		522	498	421
Earnings before income taxes and equity in earnings of subsidiaries		(277)	97	(91)
Income tax expense (benefit)		(144)	(15)	(22)
Earnings before equity in earnings of subsidiaries		(133)	112	(69)
Equity in earnings of subsidiaries	[1]	4,458	4,666	3,373
Net earnings		4,325	4,778	$ 3,304
3.625% senior notes paid May 2021
Condensed Income Statements, [Line Items]
Expense on extinguishment of debt		48
3.625% senior notes paid May 2021 | Parent Company
Condensed Income Statements, [Line Items]
Expense on extinguishment of debt		$ 48
4.00% senior notes paid January 2020
Condensed Income Statements, [Line Items]
Expense on extinguishment of debt			15
4.00% senior notes paid January 2020 | Parent Company
Condensed Income Statements, [Line Items]
Expense on extinguishment of debt			$ 15

[1] Eliminated in consolidation

[2] Includes expense of $48 in 2021 and $15 in 2020 for the early extinguishment of debt