REINSURANCE Effect of Reinsurance on Premiums and Benefits and Claims (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
Effects of Reinsurance [Line Items]
Direct premium income									$ 14,318		$ 15,025		$ 17,305
Ceded premiums									(404)		(419)		(504)
Assumed premiums earned									209		295		294
Net premium income	$ 3,385	$ 3,476	$ 3,573	$ 3,688	$ 3,523	$ 3,535	$ 3,764	$ 4,079	14,123	[1]	14,901	[1]	17,095	[1]
Direct benefits and claims, excluding reserve remeasurement									8,599		9,171		10,778
Reserve remeasurement (gains) losses									(394)		(196)		(149)
Direct benefits and claims									8,205		8,975		10,629
Reserve remeasurement (gains) losses, ceded benefits and claims									11		(19)		2
Benefits and claims, net									8,211		8,887		10,476
Intercompany eliminations
Effects of Reinsurance [Line Items]
Ceded benefits and claims									200		18		27
Assumed benefits and claims from other companies									(196)		(24)		(31)
All other
Effects of Reinsurance [Line Items]
Ceded premiums									(91)		(76)		(73)
Assumed premiums earned									83		151		114
Ceded benefits and claims									(64)		(32)		(44)
Assumed benefits and claims from other companies									220		131		109
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income									8,047		9,186		11,301
Benefits and claims, net									5,313		6,191		7,675
Aflac Japan | Closed block
Effects of Reinsurance [Line Items]
Ceded premiums									(313)		(343)		(431)
Assumed premiums earned									126		144		180
Ceded benefits and claims									(283)		(308)		(381)
Assumed benefits and claims from other companies									$ 118		$ 146		$ 165

[1] Includes a gain (loss) of $20, $(42) and $(11) in 2023, 2022 and 2021, respectively, related to remeasurement of the deferred profit liability for limited-payment contracts.