Schedule II - Aflac Incorporated (Parent Only) - Summary of Notes Payable (Detail 1) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 7,240	$ 7,295
Parent Company
Condensed Financial Statements, Captions [Line Items]
Notes payable	6,819	7,069
Parent Company | 1.125% senior notes due March 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable	398	397
Parent Company | 2.875% senior notes due October 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable	299	298
Parent Company | 3.60% senior notes due April 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	993	992
Parent Company | 6.90% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable	221	221
Parent Company | 6.45% senior notes due August 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable	254	254
Parent Company | 4.00% senior noted due October 2046
Condensed Financial Statements, Captions [Line Items]
Notes payable	394	394
Parent Company | 4.750% senior notes due January 2049
Condensed Financial Statements, Captions [Line Items]
Notes payable	542	541
Parent Company | .300% senior notes due September 2025
Condensed Financial Statements, Captions [Line Items]
Notes payable	87	93
Parent Company | .932% senior notes due January 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable	422	450
Parent Company | .500% senior notes due December 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable	88	95
Parent Company | .550% senior notes due March 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	93	99
Parent Company | 1.159% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	206	220
Parent Company | .633% senior notes due April 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable	211	225
Parent Company | .843% senior notes due December 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable	65	70
Parent Company | .750% senior notes due March 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable	145	155
Parent Company | .844% senior notes due April 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable	84	90
Parent Company | 1.488% senior notes due October 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable	106	114
Parent Company | .934% senior notes due December 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable	69	73
Parent Company | .830% senior notes due March 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable	74	79
Parent Company | 1.039% senior notes due April 2036
Condensed Financial Statements, Captions [Line Items]
Notes payable	70	75
Parent Company | 1.750% senior notes due October 2038
Condensed Financial Statements, Captions [Line Items]
Notes payable	62	66
Parent Company | 1.122% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable	44	47
Parent Company | 1.264% senior notes due April 2041
Condensed Financial Statements, Captions [Line Items]
Notes payable	70	75
Parent Company | 2.108% subordinated notes due October 2047
Condensed Financial Statements, Captions [Line Items]
Notes payable	419	448
Parent Company | 1.560% senior notes due April 2051
Condensed Financial Statements, Captions [Line Items]
Notes payable	140	149
Parent Company | 1.075% senior notes due September 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable	234	250
Parent Company | 1.320% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable	148	158
Parent Company | 1.594% senior notes due September 2037
Condensed Financial Statements, Captions [Line Items]
Notes payable	45	49
Parent Company | 2.144% senior notes due September 2052
Condensed Financial Statements, Captions [Line Items]
Notes payable	84	90
Parent Company | Yen-denominated loan variable interest rate due August 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable	82	88
Parent Company | Yen-denominated loan variable interest rate due August 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable	178	190
Parent Company | Yen-denominated loan variable interest rate due August 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 492	$ 524