Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 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)	$ (548)	$ 8,019	$ 3,113	$ 7,393	$ 6,807		$ 8,934
Retained earnings	$ 43,547			$ 41,381
Pro Forma | Accounting Standards Update 2018-12 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Retained earnings						$ (300)
Lower Limit | Pro Forma | Accounting Standards Update 2018-12 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Accumulated other comprehensive income (loss)						(18,000)
Upper Limit | Pro Forma | Accounting Standards Update 2018-12 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Accumulated other comprehensive income (loss)						$ (19,000)
Aflac Japan
Significant Accounting Policies [Line Items]
Percentage of the Company's total revenues	69.00%	69.00%
Percentage of the Company's total assets	79.00%			82.00%