BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments | segment				2
Net earned premiums		$ 4,665	$ 4,823	$ 9,303	$ 9,425
Net investment income		802	822	1,596	1,623
Total revenues		5,428	5,437	10,737	10,888
Total operating revenues		5,447	5,645	10,865	11,056
Realized investment gains (losses), non-operating	[1],[2],[3],[4],[5],[6]	(19)	(208)	(128)	(168)
Gain (loss) on change in fair value of derivative, interest rate component, operating		20	21	41	43
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		3,222	3,402	6,416	6,581
Net investment income, less amortized hedge costs	[1]	557	605	1,115	1,195
Other income (loss)		10	11	20	19
Total revenues		3,789	4,018	7,551	7,795
Hedge costs		56	37	108	69
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,388	1,362	2,778	2,729
Other income (loss)		2	0	3	3
Net investment income		180	176	358	350
Total revenues		1,570	1,538	3,139	3,082
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		72	68	144	136
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		5,431	5,624	10,834	11,013
Corporate and eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		$ 16	$ 21	$ 31	$ 43

[1] Amortized hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $56 and $37 for the three-month periods and $108 and $69 for the six-month periods ended June 30, 2017, and 2016, respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from net investment income when analyzing segment operations to conform to current year reporting.

[2] Amortized hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $56 and $37 for the three-month periods and $108 and $69 for the six-month periods ended June 30, 2017, and 2016, respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from pretax operating earnings when analyzing segment operations to conform to current year reporting.

[3] Excluding a gain of $20 and $21 for the three-month periods and $41 and $43 for the six-month periods ended June 30, 2017, and 2016, respectively, related to the interest rate component of the change in fair value of foreign currency swaps on notes payable which is classified as an operating gain when analyzing segment operations

[4] Excluding a gain of $20 and $21 for the three-month periods and $41 and $43 for the six-month periods ended June 30, 2017, and 2016, respectively, related to the interest rate component of the change in fair value of foreign currency swaps on notes payable which is classified as an operating gain when analyzing segment operations

[5] Prior year foreign currency transaction gains and losses have been reclassified from other non-operating income (loss) to realized investment gains (losses) to conform to current-year reporting classifications. These reclassifications had no impact on total earnings before income taxes.

[6] Prior year foreign currency transaction gains and losses have been reclassified from other non-operating income (loss) to realized investment gains (losses) to conform to current-year reporting classifications. These reclassifications had no impact on total revenues