STATUTORY ACCOUNTING AND DIVIDEND RESTRICTIONS - Net Income (Loss) Based on Statutory Accounting Practices (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Aflac
Statutory Accounting Practices [Line Items]
Net income (loss), statutory accounting practices	$ 872	$ 864	$ 1,331
CAIC
Statutory Accounting Practices [Line Items]
Net income (loss), statutory accounting practices	1	(16)	6
TOIC
Statutory Accounting Practices [Line Items]
Net income (loss), statutory accounting practices	(24)	(2)	0
Aflac New York
Statutory Accounting Practices [Line Items]
Net income (loss), statutory accounting practices	$ 75	$ 75	$ 67