STATUTORY ACCOUNTING AND DIVIDEND RESTRICTIONS - Capital and Surplus Based on Statutory Accounting Practices (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Aflac
Statutory Accounting Practices [Line Items]
Capital and surplus, NAIC basis	$ 2,088	$ 2,122
CAIC
Statutory Accounting Practices [Line Items]
Capital and surplus, NAIC basis	271	128
TOIC
Statutory Accounting Practices [Line Items]
Capital and surplus, NAIC basis	61	12
Aflac New York
Statutory Accounting Practices [Line Items]
Capital and surplus, NAIC basis	$ 352	$ 320