NOTES PAYABLE AND LEASE OBLIGATIONS - Summary of Lines of Credit (Details) - 3 months ended Mar. 31, 2024 ¥ in Millions, $ in Millions	USD ($)	JPY (¥)
$100 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 100.0
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	The rate quoted by the bank and agreed upon at the time of borrowing
100.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	5 years
Line of credit facility, maximum borrowing capacity | ¥		¥ 100,000
Line of credit facility, amount outstanding | ¥		0
Line of credit facility, interest rate description	A rate per annum equal to (a) Tokyo Interbank Market Rate (TIBOR) plus, the alternative applicable TIBOR margin during the availability period from the closing date to the commitment termination date or (b) the TIBOR rate offered by the agent to major banks in yen for the applicable period plus, the applicable alternative TIBOR margin during the term out period
$1 billion line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	5 years
Line of credit facility, maximum borrowing capacity	$ 1,000.0
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	A rate per annum equal to, at the Company's option, either, (a) Secured Overnight Financing Rate (SOFR) for U.S. dollar denominated borrowings or TIBOR for Japanese yen denominated borrowings, in either case adjusted for certain costs, or (b) a base rate determined by reference to the highest of (1) the federal funds rate plus 1/2 of 1%, (2) the rate of interest for such day announced by the agent as its prime rate, or (3) SOFR for an interest period of one month plus 1.00%, in each case plus an applicable margin
$50 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50.0
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	A rate per annum equal to, at the Parent Company's option, either (a) a rate determined by reference to SOFR for the interest period relevant to such borrowing or (b) the base rate determined by reference to the highest of (1) the lender's USD short-term commercial loan rate and (2) the federal funds rate plus 1/2 of 1%
$250 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 250.0
Line of credit facility, amount outstanding	$ 50.0
Line of credit facility, interest rate description	Three-month term SOFR plus a 10 basis point SOFR adjustment and an additional 75 basis points per annum
50.0 billion yen line of credit (Tranche 1)
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity | ¥		50,000
Line of credit facility, amount outstanding | ¥		0
Line of credit facility, interest rate description	Three-month yen TIBOR plus 75 basis points per annum
50.0 billion yen line of credit (Tranche 2)
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity | ¥		50,000
Line of credit facility, amount outstanding | ¥		0
Line of credit facility, interest rate description	Three-month yen TIBOR plus 75 basis points per annum
$25 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 25.0
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	Three-month term SOFR plus a 10 basis point SOFR adjustment and an additional 75 basis points per annum
$15 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 15.0
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	Three-month term SOFR plus a 10 basis point SOFR adjustment and an additional 75 basis points per annum
$300 thousand line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 0.3
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	Three-month term SOFR plus a 10 basis point SOFR adjustment and an additional 75 basis points per annum
900 million yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity | ¥		900
Line of credit facility, amount outstanding | ¥		0
Line of credit facility, interest rate description	A rate per annum equal to the short-term prime lending rates of banks appearing on the website for the Bank of Japan on the first day of the applicable period
600 million yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity | ¥		600
Line of credit facility, amount outstanding | ¥		¥ 0
Line of credit facility, interest rate description	A rate per annum equal to the short-term prime lending rates of banks appearing on the website for the Bank of Japan on the first day of the applicable period
$30 million line of credit
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 30.0
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	Three-month term SOFR plus a 10 basis point SOFR adjustment and an additional 75 basis points per annum
$400 million line of credit (Aflac Incorporated as borrower)
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 400.0
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	Three-month term SOFR plus a 10 basis point SOFR adjustment and an additional 97 basis points per annum for U.S. dollar-denominated borrowings or three-month TIBOR plus 97 basis points per annum for Japanese yen-denominated borrowings
$400 million line of credit (Aflac Re Bermuda Ltd. as borrower)
Line of Credit Facility [Line Items]
Line of credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 400.0
Line of credit facility, amount outstanding	$ 0.0
Line of credit facility, interest rate description	Three-month term SOFR plus a 10 basis point SOFR adjustment and an additional 68 basis points per annum for U.S. dollar-denominated borrowings or three-month TIBOR plus 68 basis points per annum for Japanese yen-denominated borrowings
Lower Limit | 100.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.28%
Lower Limit | $1 billion line of credit
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.08%
Upper Limit | $100 million line of credit
Line of Credit Facility [Line Items]
Debt instrument, term	3 months
Upper Limit | 100.0 billion yen line of credit
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.45%
Upper Limit | $1 billion line of credit
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.20%
Upper Limit | $50 million line of credit
Line of Credit Facility [Line Items]
Debt instrument, term	3 months