FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets by Pricing Source, Securities Carried at Amortized Cost (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	$ 17,607	$ 16,772
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	16,711	15,916
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	896	856
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Government and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	16,860	16,059
Government and agencies \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	16,711	15,916
Government and agencies \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	149	143
Government and agencies \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Government and agencies \| Third-party pricing vendor
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	16,860	16,059
Government and agencies \| Third-party pricing vendor \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	16,711	15,916
Government and agencies \| Third-party pricing vendor \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	149	143
Government and agencies \| Third-party pricing vendor \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Municipalities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	265	257
Municipalities \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Municipalities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	265	257
Municipalities \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Municipalities \| Third-party pricing vendor
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	265	257
Municipalities \| Third-party pricing vendor \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Municipalities \| Third-party pricing vendor \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	265	257
Municipalities \| Third-party pricing vendor \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Public utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	34	33
Public utilities \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Public utilities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	34	33
Public utilities \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Public utilities \| Third-party pricing vendor
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	34	33
Public utilities \| Third-party pricing vendor \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Public utilities \| Third-party pricing vendor \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	34	33
Public utilities \| Third-party pricing vendor \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Sovereign and supranational
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	430	405
Sovereign and supranational \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Sovereign and supranational \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	430	405
Sovereign and supranational \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Sovereign and supranational \| Third-party pricing vendor
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	212	198
Sovereign and supranational \| Third-party pricing vendor \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Sovereign and supranational \| Third-party pricing vendor \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	212	198
Sovereign and supranational \| Third-party pricing vendor \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Sovereign and supranational \| Internal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	218	207
Sovereign and supranational \| Internal \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Sovereign and supranational \| Internal \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	218	207
Sovereign and supranational \| Internal \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Other corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	18	18
Other corporate \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Other corporate \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	18	18
Other corporate \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Other corporate \| Third-party pricing vendor
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	18	18
Other corporate \| Third-party pricing vendor \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	0	0
Other corporate \| Third-party pricing vendor \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	18	18
Other corporate \| Third-party pricing vendor \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities, held-to-maturity, fair value	$ 0	$ 0

AFLAC INC 10-Q