STATUTORY ACCOUNTING AND DIVIDEND RESTRICTIONS - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices [Line Items]
Statutory accounting practices, statutory capital and surplus required	$ 400
Aflac
Statutory Accounting Practices [Line Items]
Capital and surplus, statutory accounting practices of the state or country basis	2,100	$ 2,600
Net Income, Nebraska state basis	864	1,300	$ 2,600
Capital and surplus, NAIC basis	2,100	2,600
Amount available for dividend distribution without prior approval from regulatory agency	864
Dividends declared	1,300
Aflac Japan
Statutory Accounting Practices [Line Items]
Capital and surplus, statutory accounting practices of the state or country basis	$ 7,800	$ 6,400