Amount, after tax, of accumulated increase (decrease) in equity from transaction and other event and circumstance from nonowner source.

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Detail) $ in Millions		9 Months Ended
	Jan. 01, 2021 USD ($)	Sep. 30, 2023 USD ($) segment	Sep. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Significant Accounting Policies [Line Items]
Number of reportable insurance business segments \| segment		2
Accumulated other comprehensive income (loss)		$ (5,760)	$ (7,505)	$ (7,338)	$ (6,429)	$ (6,980)	$ (8,411)
Retained earnings		$ 48,257			$ 44,367
Accounting Standards Update 2018-12
Significant Accounting Policies [Line Items]
Capped transition date NPR	100.00%
Accounting Standards Update 2018-12 \| Cumulative Effect, Period of Adoption, Adjustment
Significant Accounting Policies [Line Items]
Accumulated other comprehensive income (loss)	$ (18,600)
Retained earnings	$ (300)
Aflac Japan
Significant Accounting Policies [Line Items]
Percentage of the Company's total revenues		63.00%	72.00%
Percentage of the Company's total assets		79.00%			80.00%