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Number of Series of Senior Notes Issued Through a U.S. Public Debt Offering

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Face (par) amount of debt instrument at time of issuance.

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Face (par) amount of the original debt instrument that was repurchased.

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Schedule II - Aflac Incorporated (Parent Only) - Additional Information (Detail) $ in Millions, ¥ in Billions	Dec. 31, 2025 JPY (¥)	Sep. 30, 2025 JPY (¥)	Jun. 30, 2025 JPY (¥) series	May 31, 2025 JPY (¥) series	Dec. 31, 2024 JPY (¥)	Mar. 31, 2024 JPY (¥) series	Sep. 30, 2022 JPY (¥) series	Apr. 30, 2021 JPY (¥) series	Mar. 31, 2020 JPY (¥) series	Dec. 31, 2019 JPY (¥) series	Oct. 31, 2018 JPY (¥) series	Sep. 30, 2016 USD ($) series
Condensed Financial Statements, Captions [Line Items]
Number of series of senior notes issued through a U.S. public debt offering \| series			4			3	4	5	4	4	3	2
Number of series of senior notes issued through a private placement \| series				4		5
Senior notes
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount			¥ 74.9			¥ 48.6	¥ 73.0	¥ 82.0	¥ 57.0	¥ 38.0	¥ 53.4	$ 700
Private placement
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount				¥ 75.1		¥ 75.0
.300% senior notes paid September 2025
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount redeemed		¥ 12.4
Debt Instrument, Face Amount					¥ 12.4				¥ 12.4
Debt Instrument, Interest Rate, Stated Percentage		0.30%			0.30%				0.30%
1.726% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 35.0		¥ 35.0
Debt Instrument, Interest Rate, Stated Percentage	1.726%		1.726%
2.003% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 23.4		¥ 23.4
Debt Instrument, Interest Rate, Stated Percentage	2.003%		2.003%
2.369% senior notes due June 2035
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 9.5		¥ 9.5
Debt Instrument, Interest Rate, Stated Percentage	2.369%		2.369%
2.779% senior notes due June 2040
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 7.0		¥ 7.0
Debt Instrument, Interest Rate, Stated Percentage	2.779%		2.779%
1.990% senior notes due May 2032
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 18.2			¥ 18.2
Debt Instrument, Interest Rate, Stated Percentage	1.99%			1.99%
2.320% senior notes due May 2035
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 38.3			¥ 38.3
Debt Instrument, Interest Rate, Stated Percentage	2.32%			2.32%
2.650% senior notes due May 2040
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 11.6			¥ 11.6
Debt Instrument, Interest Rate, Stated Percentage	2.65%			2.65%
3.040% senior notes due May 2045
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 7.0			¥ 7.0
Debt Instrument, Interest Rate, Stated Percentage	3.04%			3.04%
Parent Company
Condensed Financial Statements, Captions [Line Items]
Number of series of senior notes issued through a U.S. public debt offering \| series			4
Number of series of senior notes issued through a private placement \| series				4
Parent Company \| Senior notes
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount			¥ 74.9
Parent Company \| Private placement
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount				¥ 75.1
Parent Company \| .300% senior notes paid September 2025
Condensed Financial Statements, Captions [Line Items]
Debt instrument, principal amount redeemed		¥ 12.4
Debt Instrument, Face Amount					¥ 12.4
Debt Instrument, Interest Rate, Stated Percentage		0.30%			0.30%
Parent Company \| 1.726% senior notes due October 2030
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 35.0		¥ 35.0
Debt Instrument, Interest Rate, Stated Percentage	1.726%		1.726%
Parent Company \| 2.003% senior notes due December 2032
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 23.4		¥ 23.4
Debt Instrument, Interest Rate, Stated Percentage	2.003%		2.003%
Parent Company \| 2.369% senior notes due June 2035
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 9.5		¥ 9.5
Debt Instrument, Interest Rate, Stated Percentage	2.369%		2.369%
Parent Company \| 2.779% senior notes due June 2040
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 7.0		¥ 7.0
Debt Instrument, Interest Rate, Stated Percentage	2.779%		2.779%
Parent Company \| 1.990% senior notes due May 2032
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 18.2			¥ 18.2
Debt Instrument, Interest Rate, Stated Percentage	1.99%			1.99%
Parent Company \| 2.320% senior notes due May 2035
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 38.3			¥ 38.3
Debt Instrument, Interest Rate, Stated Percentage	2.32%			2.32%
Parent Company \| 2.650% senior notes due May 2040
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 11.6			¥ 11.6
Debt Instrument, Interest Rate, Stated Percentage	2.65%			2.65%
Parent Company \| 3.040% senior notes due May 2045
Condensed Financial Statements, Captions [Line Items]
Debt Instrument, Face Amount	¥ 7.0			¥ 7.0
Debt Instrument, Interest Rate, Stated Percentage	3.04%			3.04%