Schedule II - Aflac Incorporated (Parent Only) - Summary of Notes Payable (Detail 1) - USD ($) $ in Millions	Dec. 31, 2021	May 31, 2021	Apr. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Apr. 30, 2020	Oct. 31, 2018	Dec. 31, 2017	Oct. 31, 2017	Sep. 30, 2017	Jan. 31, 2017	Mar. 31, 2016	Nov. 30, 2014	Jun. 30, 2013
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 7,839				$ 7,745
3.625% senior notes paid May 2021
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.625%	3.625%			3.625%									3.625%
3.625% senior notes due November 2024
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.625%				3.625%								3.625%
3.25% senior notes due March 2025
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.25%				3.25%							3.25%
1.125% senior notes due March 2026
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.125%			1.125%	1.125%
2.875% senior notes due October 2026
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.875%				2.875%					2.875%
3.60% senior notes due April 2030
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.60%				3.60%	3.60%
6.90% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.90%				6.90%			6.90%
6.45% senior notes due August 2040
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.45%				6.45%			6.45%
4.00% senior noted due October 2046
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.00%				4.00%					4.00%
4.750% senior notes due January 2049
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.75%				4.75%		4.75%
.300% senior notes due September 2025
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.30%			0.30%
.932% senior notes due January 2027
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.932%				0.932%						0.932%
.500% senior notes due December 2029
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.50%				0.50%
.550% senior notes due March 2030
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.55%			0.55%
1.159% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.159%				1.159%		1.159%
.633% senior notes due April 2031
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.633%		0.633%		0.633%
.843% senior notes due December 2031
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.843%				0.843%
.750% senior notes due March 2032
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.75%			0.75%	0.75%
.844% senior notes due April 2033
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.844%		0.844%		0.844%
1.488% senior notes due October 2033
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.488%				1.488%		1.488%
.934% senior notes due December 2034
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.934%				0.934%
.830% senior notes due March 2035
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.83%			0.83%	0.83%
1.039% senior notes due April 2036
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.039%		1.039%		1.039%
1.750% senior notes due October 2038
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.75%				1.75%		1.75%
1.122% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.122%				1.122%
1.264% senior notes due April 2041
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.264%		1.264%		1.264%
2.108% subordinated notes due October 2047
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.108%				2.108%				2.108%
1.560% senior notes due April 2051
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.56%		1.56%		1.56%
Yen-denominated loan variable interest rate due September 2026
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.41%				0.43%
Yen-denominated loan variable interest rate due September 2029
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0.56%				0.58%
Parent Company
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 7,579				$ 7,456
Parent Company | 3.625% senior notes paid May 2021
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 0				$ 698
Debt Instrument, Interest Rate, Stated Percentage	3.625%	3.625%			3.625%
Parent Company | 3.625% senior notes due November 2024
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 748				$ 747
Debt Instrument, Interest Rate, Stated Percentage	3.625%				3.625%
Parent Company | 3.25% senior notes due March 2025
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 448				$ 448
Debt Instrument, Interest Rate, Stated Percentage	3.25%				3.25%
Parent Company | 1.125% senior notes due March 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 397				$ 0
Debt Instrument, Interest Rate, Stated Percentage	1.125%			1.125%	1.125%
Parent Company | 2.875% senior notes due October 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 298				$ 298
Debt Instrument, Interest Rate, Stated Percentage	2.875%				2.875%
Parent Company | 3.60% senior notes due April 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 991				$ 990
Debt Instrument, Interest Rate, Stated Percentage	3.60%				3.60%
Parent Company | 6.90% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 221				$ 221
Debt Instrument, Interest Rate, Stated Percentage	6.90%				6.90%
Parent Company | 6.45% senior notes due August 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 255				$ 254
Debt Instrument, Interest Rate, Stated Percentage	6.45%				6.45%
Parent Company | 4.00% senior noted due October 2046
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 394				$ 394
Debt Instrument, Interest Rate, Stated Percentage	4.00%				4.00%
Parent Company | 4.750% senior notes due January 2049
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 541				$ 541
Debt Instrument, Interest Rate, Stated Percentage	4.75%				4.75%
Parent Company | .300% senior notes due September 2025
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 107				$ 119
Debt Instrument, Interest Rate, Stated Percentage	0.30%				0.30%
Parent Company | .932% senior notes due January 2027
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 520				$ 578
Debt Instrument, Interest Rate, Stated Percentage	0.932%				0.932%
Parent Company | .500% senior notes due December 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 109				$ 121
Debt Instrument, Interest Rate, Stated Percentage	0.50%				0.50%
Parent Company | .550% senior notes due March 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 115				$ 127
Debt Instrument, Interest Rate, Stated Percentage	0.55%				0.55%
Parent Company | 1.159% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 254				$ 282
Debt Instrument, Interest Rate, Stated Percentage	1.159%				1.159%
Parent Company | .633% senior notes due April 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 259				$ 0
Debt Instrument, Interest Rate, Stated Percentage	0.633%		0.633%		0.633%
Parent Company | .843% senior notes due December 2031
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 81				$ 90
Debt Instrument, Interest Rate, Stated Percentage	0.843%				0.843%
Parent Company | .750% senior notes due March 2032
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 179				$ 198
Debt Instrument, Interest Rate, Stated Percentage	0.75%				0.75%
Parent Company | .844% senior notes due April 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 104				$ 0
Debt Instrument, Interest Rate, Stated Percentage	0.844%		0.844%		0.844%
Parent Company | 1.488% senior notes due October 2033
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 131				$ 146
Debt Instrument, Interest Rate, Stated Percentage	1.488%				1.488%
Parent Company | .934% senior notes due December 2034
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 85				$ 94
Debt Instrument, Interest Rate, Stated Percentage	0.934%				0.934%
Parent Company | .830% senior notes due March 2035
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 91				$ 101
Debt Instrument, Interest Rate, Stated Percentage	0.83%				0.83%
Parent Company | 1.039% senior notes due April 2036
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 86				$ 0
Debt Instrument, Interest Rate, Stated Percentage	1.039%		1.039%		1.039%
Parent Company | 1.750% senior notes due October 2038
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 77				$ 85
Debt Instrument, Interest Rate, Stated Percentage	1.75%				1.75%
Parent Company | 1.122% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 54				$ 61
Debt Instrument, Interest Rate, Stated Percentage	1.122%				1.122%
Parent Company | 1.264% senior notes due April 2041
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 86				$ 0
Debt Instrument, Interest Rate, Stated Percentage	1.264%		1.264%		1.264%
Parent Company | 2.108% subordinated notes due October 2047
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 517				$ 575
Debt Instrument, Interest Rate, Stated Percentage	2.108%				2.108%
Parent Company | 1.560% senior notes due April 2051
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 172				$ 0
Debt Instrument, Interest Rate, Stated Percentage	1.56%		1.56%		1.56%
Parent Company | Yen-denominated loan variable interest rate due September 2026
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 43				$ 48
Debt Instrument, Interest Rate, Stated Percentage	0.41%				0.43%
Parent Company | Yen-denominated loan variable interest rate due September 2029
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 216				$ 240
Debt Instrument, Interest Rate, Stated Percentage	0.56%				0.58%