SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reconciliation of Future Policy Benefits (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	$ 83,718	$ 88,241
Deferred reinsurance gain liability	175	692
Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			$ 115,964
Deferred profit liability - limited-payment contracts			1,595
Deferred reinsurance gain liability			859
Corporate and other | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			30
Cancer | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	32,652	35,468
Cancer | Aflac Japan | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			46,854
Medical and other health | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	10,560	10,705
Medical and other health | Aflac Japan | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			14,847
Life insurance | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	23,243	24,469
Life insurance | Aflac Japan | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			31,873
Life insurance | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	911	802
Life insurance | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			1,009
Other | Aflac Japan
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	4,090	4,326
Other | Aflac Japan | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			5,736
Other | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	521	512
Other | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			684
Accident | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	621	564
Accident | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			666
Disability | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	770	810
Disability | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			1,009
Critical care | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	7,216	7,003
Critical care | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			9,365
Hospital indemnity | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	836	854
Hospital indemnity | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			1,085
Dental/vision | Aflac U.S.
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits	$ 272	$ 277
Dental/vision | Aflac U.S. | Accounting Standards Update 2018-12
Liability for Future Policy Benefit, Activity [Line Items]
Future policy benefits			$ 352