BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) segment	Jun. 30, 2015 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments | segment				2
Net earned premiums		$ 4,823	$ 4,364	$ 9,425	$ 8,796
Net investment income		822	777	1,623	1,559
Total revenues		5,437	5,287	10,888	10,513
Other non-operating income (loss)		(37)	6	(80)	(12)
Realized investment gains (losses), non-operating	[1]	(208)	104	(157)	100
Gain (loss) on change in fair value of derivative, interest rate component, operating		21	23	43	40
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		3,402	2,978	6,581	6,056
Net investment income		642	605	1,264	1,218
Other income (loss)		11	7	19	15
Total revenues		4,055	3,590	7,864	7,289
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,362	1,331	2,729	2,670
Net investment income		176	168	350	334
Other income (loss)		0	2	3	5
Total revenues		1,538	1,501	3,082	3,009
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		68	65	136	91
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		5,661	5,156	11,082	10,389
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		69	71	136	169
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		$ (48)	$ (50)	$ (93)	$ (133)

[1] Excluding a gain of $21 and $23 for the three-month periods and $43 and $40 for the six-month periods ended June 30, 2016, and 2015, 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