SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Summary of Signficant Accounting Policies - Additional Information (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)		Jan. 01, 2021 USD ($)	Jan. 01, 2020 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Significant Accounting Policies [Line Items]
Number of reportable insurance business segments | segment		2
Goodwill		$ 268	$ 269
Stockholders' Equity Attributable to Parent		33,253	33,559	$ 28,959					$ 23,462
Accumulated Other Comprehensive Income (Loss), Net of Tax		$ 7,393	$ 8,934	$ 6,615					2,151
Aflac Japan
Significant Accounting Policies [Line Items]
Percentage of the Company's total revenues		69.00%	68.00%	69.00%
Percentage of the Company's total assets		82.00%	83.00%
Accounting Standards Update 2019-04
Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle effect of adoption unrealized gain loss net of tax reclassification to accumulated other comprehensive income							$ 848
Accounting Standards Update 2019-04 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Parent	[1]			$ 848
Accumulated Other Comprehensive Income (Loss), Net of Tax				848
Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle, cumulative effect of change on liabilities								$ 134
Accounting Standards Update 2016-13 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Parent	[1]			(56)
Accounting Standards Update 2018-12 | Maximum | Cumulative effect, period of adoption, adjustment | Pro Forma
Significant Accounting Policies [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax						$ (20,000)
Accounting Standards Update 2018-12 | Lower Limit | Cumulative effect, period of adoption, adjustment | Pro Forma
Significant Accounting Policies [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax						$ (18,000)
Accumulated other comprehensive income (loss)
Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Parent		$ 7,393	$ 8,934	6,615					2,151
Accumulated other comprehensive income (loss) | Accounting Standards Update 2019-04 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Parent	[1]			848
Accumulated other comprehensive income (loss) | Accounting Standards Update 2016-13 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Parent	[1]			0
Retained earnings
Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Parent		$ 41,381	$ 37,984	34,291					$ 31,788
Retained earnings | Accounting Standards Update 2019-04 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Parent	[1]			0
Retained earnings | Accounting Standards Update 2016-13 | Cumulative effect, period of adoption, adjustment
Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Parent				$ (56)	[1]		$ 56

[1] See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2020.