Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions		9 Months Ended
		Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Jan. 01, 2021 USD ($)	Dec. 31, 2020 USD ($)
Significant Accounting Policies [Line Items]
Number of reportable insurance business segments | segment		2
Accumulated other comprehensive income (loss)		$ (3,511)	$ 7,662	$ (548)	$ 7,393	$ 8,019		$ 8,934
Retained earnings		$ 44,892			41,381
Pro Forma | Accounting Standards Update 2018-12
Significant Accounting Policies [Line Items]
Retained earnings	[1]				$ 40,963
Pro Forma | 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		72.00%	69.00%
Percentage of the Company's total assets		79.00%			82.00%

[1] Adjustment reflects the impacts from adoption of ($324) as a result of capping the net premium ratio at 100% for cohorts that are in a loss position at transition, and the decrease in current year net earnings of $(94) under the updated standard.