Schedule II - Aflac Incorporated (Parent Only) - Additional Information (Detail) $ in Millions, ¥ in Billions	1 Months Ended
	Sep. 30, 2022 JPY (¥) series	Aug. 31, 2022 JPY (¥)	Dec. 31, 2022 JPY (¥)	Oct. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2021 JPY (¥)	Apr. 30, 2021 JPY (¥)	Mar. 31, 2020 JPY (¥)	Dec. 31, 2019 JPY (¥)	Oct. 31, 2018 JPY (¥)	Mar. 31, 2017 USD ($)	Sep. 30, 2016 USD ($)	Nov. 30, 2014 USD ($)
Condensed Financial Statements, Captions [Line Items]
Number of senior notes issued | series	4
Senior notes
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 73.0						¥ 82.0	¥ 57.0	¥ 38.0	¥ 53.4		$ 700
1.039% senior notes due April 2036
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount			¥ 10.0			¥ 10.0	¥ 10.0
Debt instrument, interest rate			1.039%			1.039%	1.039%
1.075% senior notes due September 2029
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 33.4		¥ 33.4
Debt instrument, interest rate	1.075%		1.075%		1.075%
1.320% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 21.1		¥ 21.1
Debt instrument, interest rate	1.32%		1.32%		1.32%
1.594% senior notes due September 2037
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 6.5		¥ 6.5
Debt instrument, interest rate	1.594%		1.594%		1.594%
2.144% senior notes due September 2052
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 12.0		¥ 12.0
Debt instrument, interest rate	2.144%		2.144%		2.144%
Yen-denominated loans
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount		¥ 107.0
Yen-denominated loan variable interest rate due August 2027
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount		¥ 11.7	¥ 11.7
Debt instrument, interest rate			0.33%
Yen-denominated loan variable interest rate due August 2027 | Lower Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.225%
Yen-denominated loan variable interest rate due August 2027 | Upper Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.625%
Yen-denominated loan variable interest rate due August 2029
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount		¥ 25.3	¥ 25.3			¥ 5.0
Debt instrument, interest rate			0.43%			0.41%
Yen-denominated loan variable interest rate due August 2029 | Lower Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.325%
Yen-denominated loan variable interest rate due August 2029 | Upper Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.725%
Yen-denominated loan variable interest rate due August 2032
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount		¥ 70.0	¥ 70.0			¥ 25.0
Debt instrument, interest rate			0.58%			0.56%
Yen-denominated loan variable interest rate due August 2032 | Lower Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.475%
Yen-denominated loan variable interest rate due August 2032 | Upper Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		1.025%
3.25% senior notes due March 2025
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount | $											$ 450
Debt instrument, interest rate			3.25%	3.25%		3.25%					3.25%
Debt Instrument, Repurchased Face Amount | $				$ 450
3.625% senior notes due November 2024
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount | $													$ 750
Debt instrument, interest rate	3.625%		3.625%		3.625%	3.625%							3.625%
Debt Instrument, Repurchased Face Amount | $					$ 750
Parent Company
Condensed Financial Statements, Captions [Line Items]
Number of senior notes issued | series	4
Parent Company | Senior notes
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 73.0
Parent Company | 1.039% senior notes due April 2036
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount			¥ 10.0			¥ 10.0
Debt instrument, interest rate			1.039%			1.039%
Parent Company | 1.075% senior notes due September 2029
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 33.4		¥ 33.4
Debt instrument, interest rate	1.075%		1.075%		1.075%
Parent Company | 1.320% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 21.1		¥ 21.1
Debt instrument, interest rate	1.32%		1.32%		1.32%
Parent Company | 1.594% senior notes due September 2037
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 6.5		¥ 6.5
Debt instrument, interest rate	1.594%		1.594%		1.594%
Parent Company | 2.144% senior notes due September 2052
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount	¥ 12.0		¥ 12.0
Debt instrument, interest rate	2.144%		2.144%		2.144%
Parent Company | Yen-denominated loans
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount		¥ 107.0
Parent Company | Yen-denominated loan variable interest rate due August 2027
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount		¥ 11.7	¥ 11.7
Debt instrument, interest rate			0.33%
Parent Company | Yen-denominated loan variable interest rate due August 2027 | Lower Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.225%
Parent Company | Yen-denominated loan variable interest rate due August 2027 | Upper Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.625%
Parent Company | Yen-denominated loan variable interest rate due August 2029
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount		¥ 25.3	¥ 25.3			¥ 5.0
Debt instrument, interest rate			0.43%			0.41%
Parent Company | Yen-denominated loan variable interest rate due August 2029 | Lower Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.325%
Parent Company | Yen-denominated loan variable interest rate due August 2029 | Upper Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.725%
Parent Company | Yen-denominated loan variable interest rate due August 2032
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount		¥ 70.0	¥ 70.0			¥ 25.0
Debt instrument, interest rate			0.58%			0.56%
Parent Company | Yen-denominated loan variable interest rate due August 2032 | Lower Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		0.475%
Parent Company | Yen-denominated loan variable interest rate due August 2032 | Upper Limit | Tokyo Interbank Offered Rate (TIBOR)
Condensed Financial Statements, Captions [Line Items]
Debt instrument, basis spread on variable rate		1.025%
Parent Company | 3.25% senior notes due March 2025
Condensed Financial Statements, Captions [Line Items]
Debt instrument, interest rate			3.25%	3.25%		3.25%
Debt Instrument, Repurchased Face Amount | $				$ 450
Parent Company | 3.625% senior notes due November 2024
Condensed Financial Statements, Captions [Line Items]
Debt instrument, interest rate	3.625%		3.625%		3.625%	3.625%
Debt Instrument, Repurchased Face Amount | $					$ 750