Schedule II - Aflac Incorporated (Parent Only) - Summary of Notes Payable (Detail 1) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 7,295	$ 7,839
Parent Company
Condensed Financial Statements, Captions [Line Items]
Notes payable	7,069	7,579
Parent Company | 3.625% senior notes due November 2024
Condensed Financial Statements, Captions [Line Items]
Notes payable	0	748
Parent Company | 3.25% senior notes due March 2025
Condensed Financial Statements, Captions [Line Items]
Notes payable	0	448
Parent Company | 1.125% senior notes due March 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable	397	397
Parent Company | 2.875% senior notes due October 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable	298	298
Parent Company | 3.60% senior notes due April 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	992	991
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	255
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	541	541
Parent Company | .300% senior notes due September 2025
Condensed Financial Statements, Captions [Line Items]
Notes payable	93	107
Parent Company | .932% senior notes due January 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable	450	520
Parent Company | .500% senior notes due December 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable	95	109
Parent Company | .550% senior notes due March 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	99	115
Parent Company | 1.159% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	220	254
Parent Company | .633% senior notes due April 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable	225	259
Parent Company | .843% senior notes due December 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable	70	81
Parent Company | .750% senior notes due March 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable	155	179
Parent Company | .844% senior notes due April 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable	90	104
Parent Company | 1.488% senior notes due October 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable	114	131
Parent Company | .934% senior notes due December 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable	73	85
Parent Company | .830% senior notes due March 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable	79	91
Parent Company | 1.039% senior notes due April 2036
Condensed Financial Statements, Captions [Line Items]
Notes payable	75	86
Parent Company | 1.750% senior notes due October 2038
Condensed Financial Statements, Captions [Line Items]
Notes payable	66	77
Parent Company | 1.122% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable	47	54
Parent Company | 1.264% senior notes due April 2041
Condensed Financial Statements, Captions [Line Items]
Notes payable	75	86
Parent Company | 2.108% subordinated notes due October 2047
Condensed Financial Statements, Captions [Line Items]
Notes payable	448	517
Parent Company | 1.560% senior notes due April 2051
Condensed Financial Statements, Captions [Line Items]
Notes payable	149	172
Parent Company | 1.075% senior notes due September 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable	250	0
Parent Company | 1.320% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable	158	0
Parent Company | 1.594% senior notes due September 2037
Condensed Financial Statements, Captions [Line Items]
Notes payable	49	0
Parent Company | 2.144% senior notes due September 2052
Condensed Financial Statements, Captions [Line Items]
Notes payable	90	0
Parent Company | Yen-denominated loan variable interest rate due August 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable	88	0
Parent Company | Yen-denominated loan variable interest rate due August 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable	190	43
Parent Company | Yen-denominated loan variable interest rate due August 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 524	$ 216