Schedule II - Aflac Incorporated (Parent Only) - Summary of Notes Payable and Lease Obligations (Detail 1) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Condensed Financial Statements, Captions [Line Items]
Operating lease obligations	$ 73	$ 91
Notes payable and lease obligations	8,409	7,498
1.125% senior notes due March 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	400	399
2.875% senior notes due October 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	299	299
3.60% senior notes due April 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	995	994
6.90% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	221	221
6.45% senior notes due August 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	255	255
4.00% senior notes due October 2046
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	394	394
4.750% senior notes due January 2049
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	542	542
.300% senior notes paid September 2025
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	0	79
.932% senior notes due January 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	382	378
1.048% senior notes due March 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	83	81
1.075% senior notes due September 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	213	211
.500% senior notes due December 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	80	79
.550% senior notes due March 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	85	84
1.159% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	186	184
1.726% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	223	0
1.412% senior notes due March 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	178	176
.633% senior notes due April 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	191	189
.843% senior notes due December 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	59	58
.750% senior notes due March 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	131	130
1.990% senior notes due May 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	116	0
1.320% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	134	133
2.003% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	149	0
.844% senior notes due April 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	76	76
1.488% senior notes due October 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	97	95
1.682% senior notes due March 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	49	48
1.600% senior notes due March 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	116	115
.934% senior notes due December 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	62	62
.830% senior notes due March 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	67	66
2.320% senior notes due May 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	245	0
2.369% senior notes due June 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	60	0
1.740% senior notes due March 2036
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	95	94
1.039% senior notes due April 2036
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	64	63
1.594% senior notes due September 2037
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	41	41
1.750% senior notes due October 2038
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	56	56
1.920% senior notes due March 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	104	103
1.122% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	40	39
2.650% senior notes due May 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	74	0
2.779% senior notes due June 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	45	0
1.264% senior notes due April 2041
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	63	63
2.160% senior notes due March 2044
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	36	35
3.040% senior notes due May 2045
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	45	0
2.108% subordinated notes due October 2047
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	379	375
1.560% senior notes due April 2051
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	127	125
2.144% senior notes due September 2052
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	76	75
2.400% senior notes due March 2054
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	124	122
Yen-denominated loan variable interest rate due August 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	75	74
Yen-denominated loan variable interest rate due August 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	161	160
Yen-denominated loan variable interest rate due August 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	446	441
Parent Company
Condensed Financial Statements, Captions [Line Items]
Operating lease obligations	4	5
Notes payable and lease obligations	8,143	7,219
Parent Company | 1.125% senior notes due March 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	400	399
Parent Company | 2.875% senior notes due October 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	299	299
Parent Company | 3.60% senior notes due April 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	995	994
Parent Company | 6.90% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	221	221
Parent Company | 6.45% senior notes due August 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	255	255
Parent Company | 4.00% senior notes due October 2046
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	394	394
Parent Company | 4.750% senior notes due January 2049
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	542	542
Parent Company | .300% senior notes paid September 2025
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	0	79
Parent Company | .932% senior notes due January 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	382	378
Parent Company | 1.048% senior notes due March 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	83	81
Parent Company | 1.075% senior notes due September 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	213	211
Parent Company | .500% senior notes due December 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	80	79
Parent Company | .550% senior notes due March 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	85	84
Parent Company | 1.159% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	186	184
Parent Company | 1.726% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	223	0
Parent Company | 1.412% senior notes due March 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	178	176
Parent Company | .633% senior notes due April 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	191	189
Parent Company | .843% senior notes due December 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	59	58
Parent Company | .750% senior notes due March 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	131	130
Parent Company | 1.990% senior notes due May 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	116	0
Parent Company | 1.320% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	134	133
Parent Company | 2.003% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	149	0
Parent Company | .844% senior notes due April 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	76	76
Parent Company | 1.488% senior notes due October 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	97	95
Parent Company | 1.682% senior notes due March 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	49	48
Parent Company | 1.600% senior notes due March 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	116	115
Parent Company | .934% senior notes due December 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	62	62
Parent Company | .830% senior notes due March 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	67	66
Parent Company | 2.320% senior notes due May 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	245	0
Parent Company | 2.369% senior notes due June 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	60	0
Parent Company | 1.740% senior notes due March 2036
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	95	94
Parent Company | 1.039% senior notes due April 2036
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	64	63
Parent Company | 1.594% senior notes due September 2037
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	41	41
Parent Company | 1.750% senior notes due October 2038
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	56	56
Parent Company | 1.920% senior notes due March 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	104	103
Parent Company | 1.122% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	40	39
Parent Company | 2.650% senior notes due May 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	74	0
Parent Company | 2.779% senior notes due June 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	45	0
Parent Company | 1.264% senior notes due April 2041
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	63	63
Parent Company | 2.160% senior notes due March 2044
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	36	35
Parent Company | 3.040% senior notes due May 2045
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	45	0
Parent Company | 2.108% subordinated notes due October 2047
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	379	375
Parent Company | 1.560% senior notes due April 2051
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	127	125
Parent Company | 2.144% senior notes due September 2052
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	76	75
Parent Company | 2.400% senior notes due March 2054
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	124	122
Parent Company | Yen-denominated loan variable interest rate due August 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	75	74
Parent Company | Yen-denominated loan variable interest rate due August 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	161	160
Parent Company | Yen-denominated loan variable interest rate due August 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable and lease obligations	$ 446	$ 441